** Hadoop学习之路（十）HDFS API的使用：** <Excerpt in index | 首页摘要>

​ Hadoop学习之路（十）HDFS API的使用

<The rest of contents | 余下全文>

HDFS API的高级编程

HDFS的API就两个：FileSystem 和Configuration

1、文件的上传和下载

 1 package com.ghgj.hdfs.api;
 2 
 3 import org.apache.hadoop.conf.Configuration;
 4 import org.apache.hadoop.fs.FileSystem;
 5 import org.apache.hadoop.fs.Path;
 6 
 7 public class HDFS_GET_AND_PUT {
 8 
 9     public static void main(String[] args) throws Exception {
10         
11         
12         Configuration conf = new Configuration();
13         conf.set("fs.defaultFS", "hdfs://hadoop1:9000");
14         conf.set("dfs.replication", "2");
15         FileSystem fs = FileSystem.get(conf);
16         
17         
18         /**
19          * 更改操作用户有两种方式:
20          * 
21          * 1、直接设置运行换种的用户名为hadoop
22          * 
23          *     VM arguments ;   -DHADOOP_USER_NAME=hadoop
24          * 
25          * 2、在代码中进行声明
26          * 
27          *  System.setProperty("HADOOP_USER_NAME", "hadoop");
28          */
29         System.setProperty("HADOOP_USER_NAME", "hadoop");
30         
31         // 上传
32         fs.copyFromLocalFile(new Path("c:/sss.txt"), new Path("/a/ggg.txt"));
33         
34         
35         
36         /**
37          * .crc  ： 校验文件
38          * 
39          * 每个块的元数据信息都只会记录合法数据的起始偏移量：  qqq.txt  blk_41838 :  0 - 1100byte
40          * 
41          * 如果进行非法的数据追加。最终是能够下载合法数据。
42          * 由于你在数据的中间， 也就是说在 0 -1100 之间的范围进行了数据信息的更改。 造成了采用CRC算法计算出来校验值，和最初存入进HDFS的校验值
43          * 不一致。HDFS就认为当前这个文件被损坏了。
44          */
45         
46         
47         // 下载 
48         fs.copyToLocalFile(new Path("/a/qqq.txt"), new Path("c:/qqq3.txt"));
49         
50         
51         /**
52          * 上传和下载的API的底层封装其实就是 ： FileUtil.copy(....)
53          */
54         
55         fs.close();
56     }
57 }

2、配置文件conf

 1 package com.exam.hdfs;
 2 
 3 import java.io.IOException;
 4 import java.util.Iterator;
 5 import java.util.Map.Entry;
 6 
 7 import org.apache.hadoop.conf.Configuration;
 8 import org.apache.hadoop.fs.FileSystem;
 9 
10 public class TestConf1 {
11 
12     public static void main(String[] args) throws Exception {
13         
14         
15         /**
16          * 底层会加载一堆的配置文件：
17          * 
18          * core-default.xml
19          * hdfs-default.xml
20          * mapred-default.xml
21          * yarn-default.xml
22          */
23         Configuration conf = new Configuration();
24 //        conf.addResource("hdfs-default.xml");
25         
26         /**
27          * 当前这个hdfs-site.xml文件就放置在这个项目中的src下。也就是classpath路径下。
28          * 所以 FS在初始化的时候，会把hdfs-site.xml这个文件中的name-value对解析到conf中
29          * 
30          * 
31          * 但是：
32          * 
33          * 1、如果hdfs-site.xml 不在src下， 看是否能加载？？？  不能
34          * 
35          * 2、如果文件名不叫做 hdfs-default.xml 或者 hdsf-site.xml  看是否能自动加载？？？  不能
36          * 
37          * 得出的结论：
38          * 
39          * 如果需要项目代码自动加载配置文件中的信息，那么就必须把配置文件改成-default.xml或者-site.xml的名称
40          * 而且必须放置在src下
41          * 
42          * 那如果不叫这个名，或者不在src下，也需要加载这些配置文件中的参数：
43          * 
44          * 必须使用conf对象提供的一些方法去手动加载
45          */
46 //        conf.addResource("hdfs-site.xml");
47         conf.set("dfs.replication", "1");
48         conf.addResource("myconfig/hdfs-site.xml");
49         
50         
51         /**
52          * 依次加载的参数信息的顺序是：
53          * 
54          * 1、加载 core/hdfs/mapred/yarn-default.xml
55          * 
56          * 2、加载通过conf.addResources()加载的配置文件
57          * 
58          * 3、加载conf.set(name, value)
59          */
60         
61         FileSystem fs = FileSystem.get(conf);
62         
63         System.out.println(conf.get("dfs.replication"));
64 
65         
66         Iterator<Entry<String, String>> iterator = conf.iterator();
67         while(iterator.hasNext()){
68             Entry<String, String> e = iterator.next();
69             System.out.println(e.getKey() + "\t" + e.getValue());
70         }
71     }
72 }

输出结果

  1 log4j:WARN No appenders could be found for logger (org.apache.hadoop.metrics2.lib.MutableMetricsFactory).
  2 log4j:WARN Please initialize the log4j system properly.
  3 log4j:WARN See http://logging.apache.org/log4j/1.2/faq.html#noconfig for more info.
  4 1
  5 hadoop.security.groups.cache.secs    300
  6 dfs.datanode.cache.revocation.timeout.ms    900000
  7 dfs.namenode.resource.check.interval    5000
  8 s3.client-write-packet-size    65536
  9 dfs.client.https.need-auth    false
 10 dfs.replication    1
 11 hadoop.security.group.mapping.ldap.directory.search.timeout    10000
 12 dfs.datanode.available-space-volume-choosing-policy.balanced-space-threshold    10737418240
 13 hadoop.work.around.non.threadsafe.getpwuid    false
 14 dfs.namenode.write-lock-reporting-threshold-ms    5000
 15 fs.ftp.host.port    21
 16 dfs.namenode.avoid.read.stale.datanode    false
 17 dfs.journalnode.rpc-address    0.0.0.0:8485
 18 hadoop.security.kms.client.encrypted.key.cache.expiry    43200000
 19 ipc.client.connection.maxidletime    10000
 20 hadoop.registry.zk.session.timeout.ms    60000
 21 tfile.io.chunk.size    1048576
 22 fs.automatic.close    true
 23 ha.health-monitor.sleep-after-disconnect.ms    1000
 24 io.map.index.interval    128
 25 dfs.namenode.https-address    0.0.0.0:50470
 26 dfs.mover.max-no-move-interval    60000
 27 io.seqfile.sorter.recordlimit    1000000
 28 fs.s3n.multipart.uploads.enabled    false
 29 hadoop.util.hash.type    murmur
 30 dfs.namenode.replication.min    1
 31 dfs.datanode.directoryscan.threads    1
 32 dfs.namenode.fs-limits.min-block-size    1048576
 33 dfs.datanode.directoryscan.interval    21600
 34 fs.AbstractFileSystem.file.impl    org.apache.hadoop.fs.local.LocalFs
 35 dfs.namenode.acls.enabled    false
 36 dfs.client.short.circuit.replica.stale.threshold.ms    1800000
 37 net.topology.script.number.args    100
 38 hadoop.http.authentication.token.validity    36000
 39 fs.s3.block.size    67108864
 40 dfs.namenode.resource.du.reserved    104857600
 41 ha.failover-controller.graceful-fence.rpc-timeout.ms    5000
 42 s3native.bytes-per-checksum    512
 43 dfs.namenode.datanode.registration.ip-hostname-check    true
 44 dfs.namenode.path.based.cache.block.map.allocation.percent    0.25
 45 dfs.namenode.backup.http-address    0.0.0.0:50105
 46 hadoop.security.group.mapping    org.apache.hadoop.security.JniBasedUnixGroupsMappingWithFallback
 47 dfs.namenode.edits.noeditlogchannelflush    false
 48 dfs.datanode.cache.revocation.polling.ms    500
 49 dfs.namenode.audit.loggers    default
 50 hadoop.security.groups.cache.warn.after.ms    5000
 51 io.serializations    org.apache.hadoop.io.serializer.WritableSerialization,org.apache.hadoop.io.serializer.avro.AvroSpecificSerialization,org.apache.hadoop.io.serializer.avro.AvroReflectSerialization
 52 dfs.namenode.lazypersist.file.scrub.interval.sec    300
 53 fs.s3a.threads.core    15
 54 hadoop.security.crypto.buffer.size    8192
 55 hadoop.http.cross-origin.allowed-methods    GET,POST,HEAD
 56 hadoop.registry.zk.retry.interval.ms    1000
 57 dfs.http.policy    HTTP_ONLY
 58 hadoop.registry.secure    false
 59 dfs.namenode.replication.interval    3
 60 dfs.namenode.safemode.min.datanodes    0
 61 dfs.client.file-block-storage-locations.num-threads    10
 62 nfs.dump.dir    /tmp/.hdfs-nfs
 63 dfs.namenode.secondary.https-address    0.0.0.0:50091
 64 hadoop.kerberos.kinit.command    kinit
 65 dfs.block.access.token.lifetime    600
 66 dfs.webhdfs.enabled    true
 67 dfs.client.use.datanode.hostname    false
 68 dfs.namenode.delegation.token.max-lifetime    604800000
 69 fs.trash.interval    0
 70 dfs.datanode.drop.cache.behind.writes    false
 71 dfs.namenode.avoid.write.stale.datanode    false
 72 dfs.namenode.num.extra.edits.retained    1000000
 73 s3.blocksize    67108864
 74 ipc.client.connect.max.retries.on.timeouts    45
 75 dfs.datanode.data.dir    /home/hadoop/data/hadoopdata/data
 76 fs.s3.buffer.dir    ${hadoop.tmp.dir}/s3
 77 fs.s3n.block.size    67108864
 78 nfs.exports.allowed.hosts    * rw
 79 ha.health-monitor.connect-retry-interval.ms    1000
 80 hadoop.security.instrumentation.requires.admin    false
 81 hadoop.registry.zk.retry.ceiling.ms    60000
 82 nfs.rtmax    1048576
 83 dfs.client.mmap.cache.size    256
 84 dfs.datanode.data.dir.perm    700
 85 io.file.buffer.size    4096
 86 dfs.namenode.backup.address    0.0.0.0:50100
 87 dfs.client.datanode-restart.timeout    30
 88 dfs.datanode.readahead.bytes    4194304
 89 dfs.namenode.xattrs.enabled    true
 90 io.mapfile.bloom.size    1048576
 91 ipc.client.connect.retry.interval    1000
 92 dfs.client-write-packet-size    65536
 93 dfs.namenode.checkpoint.txns    1000000
 94 dfs.datanode.bp-ready.timeout    20
 95 dfs.datanode.transfer.socket.send.buffer.size    131072
 96 hadoop.security.kms.client.authentication.retry-count    1
 97 dfs.client.block.write.retries    3
 98 fs.swift.impl    org.apache.hadoop.fs.swift.snative.SwiftNativeFileSystem
 99 ha.failover-controller.graceful-fence.connection.retries    1
100 hadoop.registry.zk.connection.timeout.ms    15000
101 dfs.namenode.safemode.threshold-pct    0.999f
102 dfs.cachereport.intervalMsec    10000
103 hadoop.security.java.secure.random.algorithm    SHA1PRNG
104 ftp.blocksize    67108864
105 dfs.namenode.list.cache.directives.num.responses    100
106 dfs.namenode.kerberos.principal.pattern    *
107 file.stream-buffer-size    4096
108 dfs.datanode.dns.nameserver    default
109 fs.s3a.max.total.tasks    1000
110 dfs.namenode.replication.considerLoad    true
111 nfs.allow.insecure.ports    true
112 dfs.namenode.edits.journal-plugin.qjournal    org.apache.hadoop.hdfs.qjournal.client.QuorumJournalManager
113 dfs.client.write.exclude.nodes.cache.expiry.interval.millis    600000
114 dfs.client.mmap.cache.timeout.ms    3600000
115 ipc.client.idlethreshold    4000
116 io.skip.checksum.errors    false
117 ftp.stream-buffer-size    4096
118 fs.s3a.fast.upload    false
119 dfs.client.failover.connection.retries.on.timeouts    0
120 file.blocksize    67108864
121 ftp.replication    3
122 dfs.namenode.replication.work.multiplier.per.iteration    2
123 hadoop.security.authorization    false
124 hadoop.http.authentication.simple.anonymous.allowed    true
125 s3native.client-write-packet-size    65536
126 hadoop.rpc.socket.factory.class.default    org.apache.hadoop.net.StandardSocketFactory
127 file.bytes-per-checksum    512
128 dfs.datanode.slow.io.warning.threshold.ms    300
129 fs.har.impl.disable.cache    true
130 rpc.engine.org.apache.hadoop.hdfs.protocolPB.ClientNamenodeProtocolPB    org.apache.hadoop.ipc.ProtobufRpcEngine
131 io.seqfile.lazydecompress    true
132 dfs.namenode.reject-unresolved-dn-topology-mapping    false
133 hadoop.common.configuration.version    0.23.0
134 hadoop.security.authentication    simple
135 dfs.datanode.drop.cache.behind.reads    false
136 dfs.image.compression.codec    org.apache.hadoop.io.compress.DefaultCodec
137 dfs.client.read.shortcircuit.streams.cache.size    256
138 file.replication    1
139 dfs.namenode.top.num.users    10
140 dfs.namenode.accesstime.precision    3600000
141 dfs.namenode.fs-limits.max-xattrs-per-inode    32
142 dfs.image.transfer.timeout    60000
143 io.mapfile.bloom.error.rate    0.005
144 nfs.wtmax    1048576
145 hadoop.security.kms.client.encrypted.key.cache.size    500
146 dfs.namenode.edit.log.autoroll.check.interval.ms    300000
147 fs.s3a.multipart.purge    false
148 dfs.namenode.support.allow.format    true
149 hadoop.hdfs.configuration.version    1
150 fs.s3a.connection.establish.timeout    5000
151 hadoop.security.group.mapping.ldap.search.attr.member    member
152 dfs.secondary.namenode.kerberos.internal.spnego.principal    ${dfs.web.authentication.kerberos.principal}
153 dfs.stream-buffer-size    4096
154 hadoop.ssl.client.conf    ssl-client.xml
155 dfs.namenode.invalidate.work.pct.per.iteration    0.32f
156 fs.s3a.multipart.purge.age    86400
157 dfs.journalnode.https-address    0.0.0.0:8481
158 dfs.namenode.top.enabled    true
159 hadoop.security.kms.client.encrypted.key.cache.low-watermark    0.3f
160 dfs.namenode.max.objects    0
161 hadoop.user.group.static.mapping.overrides    dr.who=;
162 fs.s3a.fast.buffer.size    1048576
163 dfs.bytes-per-checksum    512
164 dfs.datanode.max.transfer.threads    4096
165 dfs.block.access.key.update.interval    600
166 ipc.maximum.data.length    67108864
167 tfile.fs.input.buffer.size    262144
168 ha.failover-controller.new-active.rpc-timeout.ms    60000
169 dfs.client.cached.conn.retry    3
170 dfs.client.read.shortcircuit    false
171 hadoop.ssl.hostname.verifier    DEFAULT
172 dfs.datanode.hdfs-blocks-metadata.enabled    false
173 dfs.datanode.directoryscan.throttle.limit.ms.per.sec    0
174 dfs.image.transfer.chunksize    65536
175 hadoop.http.authentication.type    simple
176 dfs.namenode.list.encryption.zones.num.responses    100
177 dfs.client.https.keystore.resource    ssl-client.xml
178 s3native.blocksize    67108864
179 net.topology.impl    org.apache.hadoop.net.NetworkTopology
180 dfs.client.failover.sleep.base.millis    500
181 io.seqfile.compress.blocksize    1000000
182 dfs.namenode.path.based.cache.refresh.interval.ms    30000
183 dfs.namenode.decommission.interval    30
184 dfs.permissions.superusergroup    supergroup
185 dfs.namenode.fs-limits.max-directory-items    1048576
186 hadoop.registry.zk.retry.times    5
187 dfs.ha.log-roll.period    120
188 fs.AbstractFileSystem.ftp.impl    org.apache.hadoop.fs.ftp.FtpFs
189 ftp.bytes-per-checksum    512
190 dfs.user.home.dir.prefix    /user
191 dfs.namenode.checkpoint.edits.dir    ${dfs.namenode.checkpoint.dir}
192 dfs.client.socket.send.buffer.size    131072
193 ipc.client.fallback-to-simple-auth-allowed    false
194 dfs.blockreport.initialDelay    0
195 dfs.namenode.inotify.max.events.per.rpc    1000
196 dfs.namenode.heartbeat.recheck-interval    300000
197 dfs.namenode.safemode.extension    30000
198 dfs.client.failover.sleep.max.millis    15000
199 dfs.namenode.delegation.key.update-interval    86400000
200 dfs.datanode.transfer.socket.recv.buffer.size    131072
201 hadoop.rpc.protection    authentication
202 fs.permissions.umask-mode    022
203 fs.s3.sleepTimeSeconds    10
204 dfs.namenode.fs-limits.max-xattr-size    16384
205 ha.health-monitor.rpc-timeout.ms    45000
206 hadoop.http.staticuser.user    dr.who
207 dfs.datanode.http.address    0.0.0.0:50075
208 fs.s3a.connection.maximum    15
209 fs.s3a.paging.maximum    5000
210 fs.AbstractFileSystem.viewfs.impl    org.apache.hadoop.fs.viewfs.ViewFs
211 dfs.namenode.blocks.per.postponedblocks.rescan    10000
212 fs.ftp.host    0.0.0.0
213 dfs.lock.suppress.warning.interval    10s
214 hadoop.http.authentication.kerberos.keytab    ${user.home}/hadoop.keytab
215 fs.s3a.impl    org.apache.hadoop.fs.s3a.S3AFileSystem
216 hadoop.registry.zk.root    /registry
217 hadoop.jetty.logs.serve.aliases    true
218 dfs.namenode.fs-limits.max-blocks-per-file    1048576
219 dfs.balancer.keytab.enabled    false
220 dfs.client.block.write.replace-datanode-on-failure.enable    true
221 hadoop.http.cross-origin.max-age    1800
222 io.compression.codec.bzip2.library    system-native
223 dfs.namenode.checkpoint.dir    file://${hadoop.tmp.dir}/dfs/namesecondary
224 dfs.client.use.legacy.blockreader.local    false
225 dfs.namenode.top.windows.minutes    1,5,25
226 ipc.ping.interval    60000
227 net.topology.node.switch.mapping.impl    org.apache.hadoop.net.ScriptBasedMapping
228 nfs.mountd.port    4242
229 dfs.storage.policy.enabled    true
230 dfs.namenode.list.cache.pools.num.responses    100
231 fs.df.interval    60000
232 nfs.server.port    2049
233 ha.zookeeper.parent-znode    /hadoop-ha
234 hadoop.http.cross-origin.allowed-headers    X-Requested-With,Content-Type,Accept,Origin
235 dfs.datanode.block-pinning.enabled    false
236 dfs.namenode.num.checkpoints.retained    2
237 fs.s3a.attempts.maximum    10
238 s3native.stream-buffer-size    4096
239 io.seqfile.local.dir    ${hadoop.tmp.dir}/io/local
240 fs.s3n.multipart.copy.block.size    5368709120
241 dfs.encrypt.data.transfer.cipher.key.bitlength    128
242 dfs.client.mmap.retry.timeout.ms    300000
243 dfs.datanode.sync.behind.writes    false
244 dfs.namenode.fslock.fair    true
245 hadoop.ssl.keystores.factory.class    org.apache.hadoop.security.ssl.FileBasedKeyStoresFactory
246 dfs.permissions.enabled    true
247 fs.AbstractFileSystem.hdfs.impl    org.apache.hadoop.fs.Hdfs
248 dfs.blockreport.split.threshold    1000000
249 dfs.datanode.balance.bandwidthPerSec    1048576
250 dfs.block.scanner.volume.bytes.per.second    1048576
251 hadoop.security.random.device.file.path    /dev/urandom
252 fs.s3.maxRetries    4
253 hadoop.http.filter.initializers    org.apache.hadoop.http.lib.StaticUserWebFilter
254 dfs.namenode.stale.datanode.interval    30000
255 ipc.client.rpc-timeout.ms    0
256 fs.client.resolve.remote.symlinks    true
257 dfs.default.chunk.view.size    32768
258 hadoop.ssl.enabled.protocols    TLSv1
259 dfs.namenode.decommission.blocks.per.interval    500000
260 dfs.namenode.handler.count    10
261 dfs.image.transfer.bandwidthPerSec    0
262 rpc.metrics.quantile.enable    false
263 hadoop.ssl.enabled    false
264 dfs.replication.max    512
265 dfs.namenode.name.dir    /home/hadoop/data/hadoopdata/name
266 dfs.namenode.read-lock-reporting-threshold-ms    5000
267 dfs.datanode.https.address    0.0.0.0:50475
268 dfs.datanode.failed.volumes.tolerated    0
269 ipc.client.kill.max    10
270 fs.s3a.threads.max    256
271 ipc.server.listen.queue.size    128
272 dfs.client.domain.socket.data.traffic    false
273 dfs.block.access.token.enable    false
274 dfs.blocksize    134217728
275 fs.s3a.connection.timeout    50000
276 fs.s3a.threads.keepalivetime    60
277 file.client-write-packet-size    65536
278 dfs.datanode.address    0.0.0.0:50010
279 ha.failover-controller.cli-check.rpc-timeout.ms    20000
280 ha.zookeeper.acl    world:anyone:rwcda
281 ipc.client.connect.max.retries    10
282 dfs.encrypt.data.transfer    false
283 dfs.namenode.write.stale.datanode.ratio    0.5f
284 ipc.client.ping    true
285 dfs.datanode.shared.file.descriptor.paths    /dev/shm,/tmp
286 dfs.short.circuit.shared.memory.watcher.interrupt.check.ms    60000
287 hadoop.tmp.dir    /home/hadoop/data/hadoopdata
288 dfs.datanode.handler.count    10
289 dfs.client.failover.max.attempts    15
290 dfs.balancer.max-no-move-interval    60000
291 dfs.client.read.shortcircuit.streams.cache.expiry.ms    300000
292 dfs.namenode.block-placement-policy.default.prefer-local-node    true
293 hadoop.ssl.require.client.cert    false
294 hadoop.security.uid.cache.secs    14400
295 dfs.client.read.shortcircuit.skip.checksum    false
296 dfs.namenode.resource.checked.volumes.minimum    1
297 hadoop.registry.rm.enabled    false
298 dfs.namenode.quota.init-threads    4
299 dfs.namenode.max.extra.edits.segments.retained    10000
300 dfs.webhdfs.user.provider.user.pattern    ^[A-Za-z_][A-Za-z0-9._-]*[$]?$
301 dfs.client.mmap.enabled    true
302 dfs.client.file-block-storage-locations.timeout.millis    1000
303 dfs.datanode.block.id.layout.upgrade.threads    12
304 dfs.datanode.use.datanode.hostname    false
305 hadoop.fuse.timer.period    5
306 dfs.client.context    default
307 fs.trash.checkpoint.interval    0
308 dfs.journalnode.http-address    0.0.0.0:8480
309 dfs.balancer.address    0.0.0.0:0
310 dfs.namenode.lock.detailed-metrics.enabled    false
311 dfs.namenode.delegation.token.renew-interval    86400000
312 ha.health-monitor.check-interval.ms    1000
313 dfs.namenode.retrycache.heap.percent    0.03f
314 ipc.client.connect.timeout    20000
315 dfs.reformat.disabled    false
316 dfs.blockreport.intervalMsec    21600000
317 fs.s3a.multipart.threshold    2147483647
318 dfs.https.server.keystore.resource    ssl-server.xml
319 hadoop.http.cross-origin.enabled    false
320 io.map.index.skip    0
321 dfs.balancer.block-move.timeout    0
322 io.native.lib.available    true
323 s3.replication    3
324 dfs.namenode.kerberos.internal.spnego.principal    ${dfs.web.authentication.kerberos.principal}
325 fs.AbstractFileSystem.har.impl    org.apache.hadoop.fs.HarFs
326 hadoop.security.kms.client.encrypted.key.cache.num.refill.threads    2
327 fs.s3n.multipart.uploads.block.size    67108864
328 dfs.image.compress    false
329 dfs.datanode.dns.interface    default
330 dfs.datanode.available-space-volume-choosing-policy.balanced-space-preference-fraction    0.75f
331 tfile.fs.output.buffer.size    262144
332 fs.du.interval    600000
333 dfs.client.failover.connection.retries    0
334 dfs.namenode.edit.log.autoroll.multiplier.threshold    2.0
335 hadoop.security.group.mapping.ldap.ssl    false
336 dfs.namenode.top.window.num.buckets    10
337 fs.s3a.buffer.dir    ${hadoop.tmp.dir}/s3a
338 dfs.namenode.checkpoint.check.period    60
339 fs.defaultFS    hdfs://hadoop1:9000
340 fs.s3a.multipart.size    104857600
341 dfs.client.slow.io.warning.threshold.ms    30000
342 dfs.datanode.max.locked.memory    0
343 dfs.namenode.retrycache.expirytime.millis    600000
344 hadoop.security.group.mapping.ldap.search.attr.group.name    cn
345 dfs.client.block.write.replace-datanode-on-failure.best-effort    false
346 dfs.ha.fencing.ssh.connect-timeout    30000
347 dfs.datanode.scan.period.hours    504
348 hadoop.registry.zk.quorum    localhost:2181
349 dfs.namenode.fs-limits.max-component-length    255
350 hadoop.http.cross-origin.allowed-origins    *
351 dfs.namenode.enable.retrycache    true
352 dfs.datanode.du.reserved    0
353 dfs.datanode.ipc.address    0.0.0.0:50020
354 hadoop.registry.system.acls    sasl:yarn@, sasl:mapred@, sasl:hdfs@
355 dfs.namenode.path.based.cache.retry.interval.ms    30000
356 hadoop.security.crypto.cipher.suite    AES/CTR/NoPadding
357 dfs.client.block.write.replace-datanode-on-failure.policy    DEFAULT
358 dfs.namenode.http-address    0.0.0.0:50070
359 hadoop.security.crypto.codec.classes.aes.ctr.nopadding    org.apache.hadoop.crypto.OpensslAesCtrCryptoCodec,org.apache.hadoop.crypto.JceAesCtrCryptoCodec
360 dfs.ha.tail-edits.period    60
361 hadoop.security.groups.negative-cache.secs    30
362 hadoop.ssl.server.conf    ssl-server.xml
363 hadoop.registry.jaas.context    Client
364 s3native.replication    3
365 hadoop.security.group.mapping.ldap.search.filter.group    (objectClass=group)
366 hadoop.http.authentication.kerberos.principal    HTTP/_HOST@LOCALHOST
367 dfs.namenode.startup.delay.block.deletion.sec    0
368 hadoop.security.group.mapping.ldap.search.filter.user    (&(objectClass=user)(sAMAccountName={0}))
369 dfs.namenode.edits.dir    ${dfs.namenode.name.dir}
370 dfs.namenode.checkpoint.max-retries    3
371 s3.stream-buffer-size    4096
372 ftp.client-write-packet-size    65536
373 dfs.datanode.fsdatasetcache.max.threads.per.volume    4
374 hadoop.security.sensitive-config-keys    password$,fs.s3.*[Ss]ecret.?[Kk]ey,fs.azure.account.key.*,dfs.webhdfs.oauth2.[a-z]+.token,hadoop.security.sensitive-config-keys
375 dfs.namenode.decommission.max.concurrent.tracked.nodes    100
376 dfs.namenode.name.dir.restore    false
377 ipc.server.log.slow.rpc    false
378 dfs.heartbeat.interval    3
379 dfs.namenode.secondary.http-address    hadoop3:50090
380 ha.zookeeper.session-timeout.ms    5000
381 s3.bytes-per-checksum    512
382 fs.s3a.connection.ssl.enabled    true
383 hadoop.http.authentication.signature.secret.file    ${user.home}/hadoop-http-auth-signature-secret
384 hadoop.fuse.connection.timeout    300
385 dfs.namenode.checkpoint.period    3600
386 ipc.server.max.connections    0
387 dfs.ha.automatic-failover.enabled    false

3、列出指定目录下的文件以及块的信息

 1 package com.exam.hdfs;
 2 
 3 import org.apache.hadoop.conf.Configuration;
 4 import org.apache.hadoop.fs.BlockLocation;
 5 import org.apache.hadoop.fs.FileSystem;
 6 import org.apache.hadoop.fs.LocatedFileStatus;
 7 import org.apache.hadoop.fs.Path;
 8 import org.apache.hadoop.fs.RemoteIterator;
 9 
10 public class TestHDFS1 {
11 
12     public static void main(String[] args) throws Exception {
13 
14         Configuration conf = new Configuration();
15         System.setProperty("HADOOP_USER_NAME", "hadoop");
16         conf.set("fs.defaultFS", "hdfs://hadoop1:9000");
17         FileSystem fs = FileSystem.get(conf);
18 
19         /**
20          * 列出指定的目录下的所有文件
21          */
22         RemoteIterator<LocatedFileStatus> listFiles = fs.listFiles(new Path("/"), true);
23         while(listFiles.hasNext()){
24             LocatedFileStatus file = listFiles.next();
25             
26             
27             System.out.println(file.getPath()+"\t");
28             System.out.println(file.getPath().getName()+"\t");
29             System.out.println(file.getLen()+"\t");
30             System.out.println(file.getReplication()+"\t");
31             
32             /**
33              * blockLocations的长度是几？  是什么意义？
34              * 
35              * 块的数量
36              */
37             BlockLocation[] blockLocations = file.getBlockLocations();
38             System.out.println(blockLocations.length+"\t");
39             
40             for(BlockLocation bl : blockLocations){
41                 String[] hosts = bl.getHosts();
42                 
43                 System.out.print(hosts[0] + "-" + hosts[1]+"\t");
44             }
45             System.out.println();
46             
47         }
48         
49         
50     }
51 }

输出结果

1 hdfs://hadoop1:9000/aa/bb/cc/hadoop.tar.gz    
2 hadoop.tar.gz    
3 199007110    
4 2    
5 3    
6 hadoop3-hadoop1    hadoop1-hadoop2    hadoop1-hadoop4

4、上传文件

 1 package com.exam.hdfs;
 2 
 3 import java.io.File;
 4 import java.io.FileInputStream;
 5 import java.io.InputStream;
 6 
 7 import org.apache.hadoop.conf.Configuration;
 8 import org.apache.hadoop.fs.FSDataOutputStream;
 9 import org.apache.hadoop.fs.FileSystem;
10 import org.apache.hadoop.fs.Path;
11 import org.apache.hadoop.io.IOUtils;
12 
13 public class UploadDataByStream {
14 
15     public static void main(String[] args) throws Exception {
16         
17         
18         Configuration conf = new Configuration();
19         System.setProperty("HADOOP_USER_NAME", "hadoop");
20         conf.set("fs.defaultFS", "hdfs://hadoop1:9000");
21         FileSystem fs = FileSystem.get(conf);
22         
23         
24         InputStream in = new FileInputStream(new File("d:/abc.tar.gz"));
25         FSDataOutputStream out = fs.create(new Path("/aa/abc.tar.gz"));
26         
27         
28         IOUtils.copyBytes(in, out, 4096, true);
29         
30         fs.close();
31         
32     }
33 }

5、下载文件

 1 package com.exam.hdfs;
 2 
 3 import java.io.File;
 4 import java.io.FileOutputStream;
 5 import java.io.OutputStream;
 6 
 7 import org.apache.hadoop.conf.Configuration;
 8 import org.apache.hadoop.fs.FSDataInputStream;
 9 import org.apache.hadoop.fs.FileSystem;
10 import org.apache.hadoop.fs.Path;
11 import org.apache.hadoop.io.IOUtils;
12 
13 public class DownloadDataByStream {
14 
15     
16     public static void main(String[] args) throws Exception {
17         
18         Configuration conf = new Configuration();
19         System.setProperty("HADOOP_USER_NAME", "hadoop");
20         conf.set("fs.defaultFS", "hdfs://hadoop1:9000");
21         FileSystem fs = FileSystem.get(conf);
22         
23         
24         FSDataInputStream in = fs.open(new Path("/aa/abc.tar.gz"));
25         OutputStream out = new FileOutputStream(new File("D:/abc.sh"));
26         
27         
28         IOUtils.copyBytes(in, out, 4096, true);
29         
30         fs.close();
31         
32     }
33 }

6、删除某个路径下特定类型的文件，比如class类型文件，比如txt类型文件

 1 package com.exam.hdfs;
 2 
 3 import java.net.URI;
 4 
 5 import org.apache.hadoop.conf.Configuration;
 6 import org.apache.hadoop.fs.FileStatus;
 7 import org.apache.hadoop.fs.FileSystem;
 8 import org.apache.hadoop.fs.Path;
 9 
10 public class HDFS_DELETE_CLASS {
11     
12     public static final String FILETYPE = "tar.gz";
13     public static final String DELETE_PATH = "/aa";
14     
15     public static void main(String[] args) throws Exception {
16         
17         new HDFS_DELETE_CLASS().rmrClassFile(new Path(DELETE_PATH));
18     }
19     
20     public void rmrClassFile(Path path) throws Exception{
21         
22         // 首先获取集群必要的信息，以得到FileSystem的示例对象fs
23         Configuration conf = new Configuration();
24         FileSystem fs = FileSystem.get(new URI("hdfs://hadoop1:9000"), conf, "hadoop");
25         
26         // 首先检查path本身是文件夹还是目录
27         FileStatus fileStatus = fs.getFileStatus(path);
28         boolean directory = fileStatus.isDirectory();
29         
30         // 根据该目录是否是文件或者文件夹进行相应的操作
31         if(directory){
32             // 如果是目录
33             checkAndDeleteDirectory(path, fs);
34         }else{
35             // 如果是文件，检查该文件名是不是FILETYPE类型的文件
36             checkAndDeleteFile(path, fs);
37         }
38     }
39     
40     // 处理目录
41     public static void checkAndDeleteDirectory(Path path, FileSystem fs) throws Exception{
42         // 查看该path目录下一级子目录和子文件的状态
43         FileStatus[] listStatus = fs.listStatus(path);
44         for(FileStatus fStatus: listStatus){
45             Path p = fStatus.getPath();
46             // 如果是文件，并且是以FILETYPE结尾，则删掉，否则继续遍历下一级目录
47             if(fStatus.isFile()){
48                 checkAndDeleteFile(p, fs);
49             }else{
50                 checkAndDeleteDirectory(p, fs);
51             }
52         }
53     }
54     
55     // 檢查文件是否符合刪除要求，如果符合要求則刪除，不符合要求则不做处理
56     public static void checkAndDeleteFile(Path path, FileSystem fs) throws Exception{
57         String name = path.getName();
58         System.out.println(name);
59         /*// 直接判断有没有FILETYPE这个字符串,不是特别稳妥，并且会有误操作，所以得判断是不是以FILETYPE结尾
60         if(name.indexOf(FILETYPE) != -1){
61             fs.delete(path, true);
62         }*/
63         // 判断是不是以FILETYPE结尾
64         int startIndex = name.length() - FILETYPE.length();
65         int endIndex = name.length();
66         // 求得文件后缀名
67         String fileSuffix = name.substring(startIndex, endIndex);
68         if(fileSuffix.equals(FILETYPE)){
69             fs.delete(path, true);
70         }
71     }
72 }

7、删除HDFS集群中的所有空文件和空目录

  1 public class DeleteEmptyDirAndFile {
  2     
  3     static FileSystem fs = null;
  4 
  5     public static void main(String[] args) throws Exception {
  6         
  7         initFileSystem();
  8 
  9 //         创建测试数据
 10 //        makeTestData();
 11 
 12         // 删除测试数据
 13 //        deleteTestData();
 14 
 15         // 删除指定文件夹下的空文件和空文件夹
 16         deleteEmptyDirAndFile(new Path("/aa"));
 17     }
 18     
 19     /**
 20      * 删除指定文件夹下的 空文件 和 空文件夹
 21      * @throws Exception 
 22      */
 23     public static void deleteEmptyDirAndFile(Path path) throws Exception {
 24         
 25         //当是空文件夹时
 26         FileStatus[] listStatus = fs.listStatus(path);
 27         if(listStatus.length == 0){
 28             fs.delete(path, true);
 29             return;
 30         }
 31         
 32         // 该方法的结果：包括指定目录的  文件 和 文件夹
 33         RemoteIterator<LocatedFileStatus> listLocatedStatus = fs.listLocatedStatus(path);
 34         
 35         while (listLocatedStatus.hasNext()) {
 36             LocatedFileStatus next = listLocatedStatus.next();
 37 
 38             Path currentPath = next.getPath();
 39             // 获取父目录
 40             Path parent = next.getPath().getParent();
 41             
 42             // 如果是文件夹，继续往下遍历，删除符合条件的文件（空文件夹）
 43             if (next.isDirectory()) {
 44                 
 45                 // 如果是空文件夹
 46                 if(fs.listStatus(currentPath).length == 0){
 47                     // 删除掉
 48                     fs.delete(currentPath, true);
 49                 }else{
 50                     // 不是空文件夹，那么则继续遍历
 51                     if(fs.exists(currentPath)){
 52                         deleteEmptyDirAndFile(currentPath);
 53                     }
 54                 }
 55                 
 56             // 如果是文件
 57             } else {
 58                 // 获取文件的长度
 59                 long fileLength = next.getLen();
 60                 // 当文件是空文件时， 删除
 61                 if(fileLength == 0){
 62                     fs.delete(currentPath, true);
 63                 }
 64             }
 65             
 66             // 当空文件夹或者空文件删除时，有可能导致父文件夹为空文件夹，
 67             // 所以每次删除一个空文件或者空文件的时候都需要判断一下，如果真是如此，那么就需要把该文件夹也删除掉
 68             int length = fs.listStatus(parent).length;
 69             if(length == 0){
 70                 fs.delete(parent, true);
 71             }
 72         }
 73     }
 74     
 75     /**
 76      * 初始化FileSystem对象之用
 77      */
 78     public static void initFileSystem() throws Exception{
 79         Configuration conf = new Configuration();
 80         System.setProperty("HADOOP_USER_NAME", "hadoop");
 81         conf.addResource("config/core-site.xml");
 82         conf.addResource("config/hdfs-site.xml");
 83         fs = FileSystem.get(conf);
 84     }
 85 
 86     /**
 87      * 创建 测试 数据之用
 88      */
 89     public static void makeTestData() throws Exception {
 90         
 91         String emptyFilePath = "D:\\bigdata\\1704mr_test\\empty.txt";
 92         String notEmptyFilePath = "D:\\bigdata\\1704mr_test\\notEmpty.txt";
 93 
 94         // 空文件夹 和 空文件 的目录
 95         String path1 = "/aa/bb1/cc1/dd1/";
 96         fs.mkdirs(new Path(path1));
 97         fs.mkdirs(new Path("/aa/bb1/cc1/dd2/"));
 98         fs.copyFromLocalFile(new Path(emptyFilePath), new Path(path1));
 99         fs.copyFromLocalFile(new Path(notEmptyFilePath), new Path(path1));
100 
101         // 空文件 的目录
102         String path2 = "/aa/bb1/cc2/dd2/";
103         fs.mkdirs(new Path(path2));
104         fs.copyFromLocalFile(new Path(emptyFilePath), new Path(path2));
105 
106         // 非空文件 的目录
107         String path3 = "/aa/bb2/cc3/dd3";
108         fs.mkdirs(new Path(path3));
109         fs.copyFromLocalFile(new Path(notEmptyFilePath), new Path(path3));
110 
111         // 空 文件夹
112         String path4 = "/aa/bb2/cc4/dd4";
113         fs.mkdirs(new Path(path4));
114 
115         System.out.println("测试数据创建成功");
116     }
117 
118     /**
119      * 删除 指定文件夹
120      * @throws Exception 
121      */
122     public static void deleteTestData() throws Exception {
123         boolean delete = fs.delete(new Path("/aa"), true);
124         System.out.println(delete ? "删除数据成功" : "删除数据失败");
125     }
126 
127 }

8、手动拷贝某个特定的数据块（比如某个文件的第二个数据块）

 1 /**
 2      * 手动拷贝某个特定的数据块（比如某个文件的第二个数据块）
 3      * */
 4     public static void copyBlock(String str,int num) {
 5         
 6         Path path = new Path(str);
 7         
 8         BlockLocation[] localtions = new BlockLocation[0] ;
 9         
10         try {
11             FileStatus fileStatus = fs.getFileStatus(path);
12             
13             localtions = fs.getFileBlockLocations(fileStatus, 0, fileStatus.getLen());
14             
15             /*for(int i=0;i<localtions.length;i++) {
16                 //0,134217728,hadoop1,hadoop3
17                 //134217728,64789382,hadoop3,hadoop1
18                 System.out.println(localtions[i]);
19             }*/
20             
21             /*System.out.println(localtions[num-1].getOffset());
22             System.out.println(localtions[num-1].getLength());
23             String[] hosts = localtions[num-1].getHosts();*/
24             
25             FSDataInputStream open = fs.open(path);
26             open.seek(localtions[num-1].getOffset());
27             OutputStream out = new FileOutputStream(new File("D:/abc.tar.gz"));
28             IOUtils.copyBytes(open, out,4096,true);
29             
30             
31             
32         } catch (IOException e) {
33             e.printStackTrace();
34         }
35         
36     }

9、编写程序统计出HDFS文件系统中文件大小小于HDFS集群中的默认块大小的文件占比

 1 import org.apache.hadoop.conf.Configuration;
 2 import org.apache.hadoop.fs.FileSystem;
 3 import org.apache.hadoop.fs.LocatedFileStatus;
 4 import org.apache.hadoop.fs.Path;
 5 import org.apache.hadoop.fs.RemoteIterator;
 6 
 7 /**
 8  * 
 9  * 编写程序统计出HDFS文件系统中文件大小小于HDFS集群中的默认块大小的文件占比
10  * 比如：大于等于128M的文件个数为98，小于128M的文件总数为2，所以答案是2%
11  */
12 public class Exam1_SmallFilePercent {
13     
14     private static int DEFAULT_BLOCKSIZE = 128 * 1024 * 1024;
15 
16     public static void main(String[] args) throws Exception {
17         
18         
19         Configuration conf = new Configuration();
20         conf.set("fs.defaultFS", "hdfs://hadoop1:9000");
21         System.setProperty("HADOOP_USER_NAME", "hadoop");
22         FileSystem fs = FileSystem.get(conf);
23         
24         
25         Path path = new Path("/");
26         float smallFilePercent = getSmallFilePercent(fs, path);
27         System.out.println(smallFilePercent);
28         
29         
30         fs.close();
31     }
32 
33     /**
34      * 该方法求出指定目录下的小文件和总文件数的对比
35      * @throws Exception 
36      */
37     private static float getSmallFilePercent(FileSystem fs, Path path) throws Exception {
38         // TODO Auto-generated method stub
39         
40         int smallFile = 0;
41         int totalFile = 0;
42         
43         RemoteIterator<LocatedFileStatus> listFiles = fs.listFiles(path, false);
44         while(listFiles.hasNext()){
45             totalFile++;
46             LocatedFileStatus next = listFiles.next();
47             long len = next.getLen();
48             if(len < DEFAULT_BLOCKSIZE){
49                 smallFile++;
50             }
51         }
52         System.out.println(smallFile+" : "+totalFile);
53         
54         return smallFile * 1f /totalFile;
55     }
56     
57 }

10、编写程序统计出HDFS文件系统中的平均数据块数（数据块总数/文件总数）

 1 import org.apache.hadoop.conf.Configuration;
 2 import org.apache.hadoop.fs.FileSystem;
 3 import org.apache.hadoop.fs.LocatedFileStatus;
 4 import org.apache.hadoop.fs.Path;
 5 import org.apache.hadoop.fs.RemoteIterator;
 6 
 7 /**
 8  * 
 9  * 编写程序统计出HDFS文件系统中的平均数据块数（数据块总数/文件总数）
10  * 比如：一个文件有5个块，一个文件有3个块，那么平均数据块数为4
11  * 如果还有一个文件，并且数据块就1个，那么整个HDFS的平均数据块数就是3
12  */
13 public class Exam2_HDSFAvgBlocks {
14     
15     public static void main(String[] args) throws Exception {
16         
17         
18         Configuration conf = new Configuration();
19         conf.set("fs.defaultFS", "hdfs://hadoop1:9000");
20         System.setProperty("HADOOP_USER_NAME", "hadoop");
21         FileSystem fs = FileSystem.get(conf);
22         
23         
24         Path path = new Path("/");
25         float avgHDFSBlocks = getHDFSAvgBlocks(fs, path);
26         System.out.println("HDFS的平均数据块个数为：" + avgHDFSBlocks);
27         
28         
29         fs.close();
30     }
31 
32     /**
33      * 求出指定目录下的所有文件的平均数据块个数
34      */
35     private static float getHDFSAvgBlocks(FileSystem fs, Path path) throws Exception {
36         // TODO Auto-generated method stub
37         
38         int totalFiles = 0;        // 总文件数
39         int totalBlocks = 0;    // 总数据块数
40         
41         RemoteIterator<LocatedFileStatus> listFiles = fs.listFiles(path, false);
42         
43         while(listFiles.hasNext()){
44             LocatedFileStatus next = listFiles.next();
45             int length = next.getBlockLocations().length;
46             totalBlocks += length;
47             if(next.getLen() != 0){
48                 totalFiles++;
49             }
50         }
51         System.out.println(totalBlocks+" : "+totalFiles);
52         
53         return totalBlocks * 1f / totalFiles;
54     }
55     
56 }

11、编写程序统计出HDFS文件系统中的平均副本数（副本总数/总数据块数）

 1 import org.apache.hadoop.conf.Configuration;
 2 import org.apache.hadoop.fs.FileSystem;
 3 import org.apache.hadoop.fs.LocatedFileStatus;
 4 import org.apache.hadoop.fs.Path;
 5 import org.apache.hadoop.fs.RemoteIterator;
 6 
 7 /**
 8  * 编写程序统计出HDFS文件系统中的平均副本数（副本总数/总数据块数）
 9  * 比如：总共两个文件，一个文件5个数据块，每个数据块3个副本，第二个文件2个数据块，每个文件2个副本，最终的平均副本数 = （3*3 + 2*2）/（3+2）= 2.8
10  */
11 public class Exam3_HDSFAvgBlockCopys {
12     
13     public static void main(String[] args) throws Exception {
14         
15         
16         Configuration conf = new Configuration();
17         conf.set("fs.defaultFS", "hdfs://hadoop02:9000");
18         System.setProperty("HADOOP_USER_NAME", "hadoop");
19         FileSystem fs = FileSystem.get(conf);
20         
21         
22         Path path = new Path("/");
23         float avgHDFSBlockCopys = getHDFSAvgBlockCopys(fs, path);
24         System.out.println("HDFS的平均数据块个数为：" + avgHDFSBlockCopys);
25         
26         
27         fs.close();
28     }
29 
30     /**
31      * 求出指定目录下的所有文件的平均数据块个数
32      */
33     private static float getHDFSAvgBlockCopys(FileSystem fs, Path path) throws Exception {
34         // TODO Auto-generated method stub
35         
36         int totalCopy = 0;        // 总副本数
37         int totalBlocks = 0;    // 总数据块数
38         
39         RemoteIterator<LocatedFileStatus> listFiles = fs.listFiles(path, false);
40         
41         while(listFiles.hasNext()){
42             LocatedFileStatus next = listFiles.next();
43 
44             int length = next.getBlockLocations().length;
45             short replication = next.getReplication();
46             
47             totalBlocks += length;
48             totalCopy += length * replication;
49         }
50         System.out.println(totalCopy+" : "+totalBlocks);
51         
52         return totalCopy * 1f / totalBlocks;
53     }
54     
55 }

12、统计HDFS整个文件系统中的不足指定数据块大小的数据块的比例

 1 import java.io.IOException;
 2 
 3 import org.apache.hadoop.conf.Configuration;
 4 import org.apache.hadoop.fs.BlockLocation;
 5 import org.apache.hadoop.fs.FileSystem;
 6 import org.apache.hadoop.fs.LocatedFileStatus;
 7 import org.apache.hadoop.fs.Path;
 8 import org.apache.hadoop.fs.RemoteIterator;
 9 
10 /**
11  * 统计HDFS整个文件系统中的不足指定数据块大小的数据块的比例
12  * 比如指定的数据块大小是128M，总数据块有100个，不是大小为完整的128M的数据块有5个，那么不足指定数据块大小的数据块的比例就为5%
13  * 注意：千万注意考虑不同文件的指定数据块大小可能不一致。所以千万不能用默认的128M一概而论
14  */
15 public class Exam4_LTBlockSize {
16 
17     public static void main(String[] args) throws Exception {
18         
19         Configuration conf = new Configuration();
20         conf.set("fs.defaultFS", "hdfs://hadoop02:9000");
21         System.setProperty("HADOOP_USER_NAME", "hadoop");
22         FileSystem fs = FileSystem.get(conf);
23         
24         Path path = new Path("/");
25         float avgHDFSBlockCopys = getLessThanBlocksizeBlocks(fs, path);
26         System.out.println("HDFS的不足指定数据块大小的数据块数目为：" + avgHDFSBlockCopys);
27         
28         fs.close();
29     }
30 
31     private static float getLessThanBlocksizeBlocks(FileSystem fs, Path path) throws Exception {
32         // TODO Auto-generated method stub
33         
34         int totalBlocks = 0;                // 总副本数
35         int lessThenBlocksizeBlocks = 0;    // 总数据块数
36         
37         RemoteIterator<LocatedFileStatus> listFiles = fs.listFiles(path, false);
38         
39         while(listFiles.hasNext()){
40             LocatedFileStatus next = listFiles.next();
41 
42             BlockLocation[] blockLocations = next.getBlockLocations();
43             int length = blockLocations.length;
44             
45             if(length != 0){
46                 totalBlocks += length;
47                 long lastBlockSize = blockLocations[length - 1].getLength();
48                 long blockSize = next.getBlockSize();
49                 if(lastBlockSize < blockSize){
50                     lessThenBlocksizeBlocks++;
51                 }
52             }
53         }
54         System.out.println(lessThenBlocksizeBlocks+" : "+totalBlocks);
55         
56         return lessThenBlocksizeBlocks * 1f / totalBlocks;
57     }
58 }

13、统计出一个给定数组的蓄水总量（把数组的每个位置的数看是做地势高低）

  1 /**
  2         统计出一个给定数组的蓄水总量（把数组的每个位置的数看是做地势高低）
  3         比如：int[] intArray = new int[]{4,3,2,5,6,4,4,7}
  4         能蓄水：[0,1,2,0,0,2,2,0] 所以总量是：7
  5         
  6     核心思路：把数组切成很多个 01数组，每一层一个01数组，统计每个01数组中的合法0的总个数（数组的左边第一个1的中间区间中的0的个数）即可
  7  */
  8 public class Exam5_WaterStoreOfArray {
  9 
 10     public static void main(String[] args) {
 11         
 12 //        int[] intArray = new int[]{4,3,2,5,6,4,4,7};
 13 //        int[] intArray = new int[]{1,2,3,4,5,6};
 14         int[] intArray = new int[]{3,1,2,7,3,8,4,9,5,6};
 15         
 16         int totalWater = getArrayWater(intArray);
 17         System.out.println(totalWater);
 18     }
 19     
 20     /**
 21      * 求出数组中的水数
 22      */
 23     private static int getArrayWater(int[] intArray) {
 24         
 25         int findMaxValueOfArray = findMaxValueOfArray(intArray);
 26         int findMinValueOfArray = findMinValueOfArray(intArray);
 27         int length = intArray.length;
 28         
 29         int totalWater = 0;
 30         
 31         // 循环次数就是最大值和最小值的差
 32         for(int i=findMinValueOfArray; i<findMaxValueOfArray; i++){
 33             // 循环构造每一层的01数组
 34             int[] tempArray = new int[length];
 35             for(int j=0; j<length; j++){
 36                 if(intArray[j] > i){
 37                     tempArray[j] = 1;
 38                 }else{
 39                     tempArray[j] = 0;
 40                 }
 41             }
 42             // 获取每一个01数组的合法0个数
 43             int waterOfOneZeroArray = getWaterOfOneZeroArray(tempArray);
 44             totalWater += waterOfOneZeroArray;
 45         }
 46         return totalWater;
 47     }
 48     
 49 
 50     /**
 51      * 寻找逻辑是：从左右开始各找一个1，然后这两个1之间的所有0的个数，就是水数
 52      */
 53     private static int getWaterOfOneZeroArray(int[] tempArray) {
 54         
 55         int length = tempArray.length;
 56         int toatalWater = 0;
 57         
 58         // 找左边的1
 59         int i = 0;
 60         while(i < length){
 61             if(tempArray[i] == 1){
 62                 break;
 63             }
 64             i++;
 65         }
 66         
 67         // 从右边开始找1
 68         int j=length-1;
 69         while(j >= i){
 70             if(tempArray[j] == 1){
 71                 break;
 72             }
 73             j--;
 74         }
 75         
 76         // 找以上两个1之间的0的个数。
 77         if(i == j || i + 1 == j){
 78             return 0;
 79         }else{
 80             for(int k=i+1; k<j; k++){
 81                 if(tempArray[k] == 0){
 82                     toatalWater++;
 83                 }
 84             }
 85             return toatalWater;
 86         }
 87     }
 88 
 89     /**
 90      * 
 91      * 描述：找出一个数组中的最大值
 92      */
 93     public static int findMaxValueOfArray(int[] intArray){
 94         int length = intArray.length;
 95         if(length == 0){
 96             return 0;
 97         }else if(length == 1){
 98             return intArray[0];
 99         }else{
100             int max = intArray[0];
101             for(int i=1; i<length; i++){
102                 if(intArray[i] > max){
103                     max = intArray[i];
104                 }
105             }
106             return max;
107         }
108     }
109     
110     /**
111      * 找出一个数组中的最小值
112      */
113     public static int findMinValueOfArray(int[] intArray){
114         int length = intArray.length;
115         if(length == 0){
116             return 0;
117         }else if(length == 1){
118             return intArray[0];
119         }else{
120             int min = intArray[0];
121             for(int i=1; i<length; i++){
122                 if(intArray[i] < min){
123                     min = intArray[i];
124                 }
125             }
126             return min;
127         }
128     }
129 }