Question

我是Java的新手，特别是Java中的面向对象编程，我不断收到这个让我疯狂的错误。

以下是我的员工超类的一部分：

16/01/30 20:45:15 WARN util.NativeCodeLoader: Unable to load native-hadoop library for your platform... using builtin-java classes where applicable
16/01/30 20:45:16 INFO Configuration.deprecation: session.id is deprecated. Instead, use dfs.metrics.session-id
16/01/30 20:45:16 INFO jvm.JvmMetrics: Initializing JVM Metrics with processName=JobTracker, sessionId=
16/01/30 20:45:16 WARN mapreduce.JobSubmitter: Hadoop command-line option parsing not performed. Implement the Tool interface and execute your application with ToolRunner to remedy this.
16/01/30 20:45:16 INFO input.FileInputFormat: Total input paths to process : 1
16/01/30 20:45:16 INFO input.FileInputFormat: Total input paths to process : 1
16/01/30 20:45:16 INFO mapreduce.JobSubmitter: number of splits:3
16/01/30 20:45:17 INFO mapreduce.JobSubmitter: Submitting tokens for job: job_local1787244132_0001
16/01/30 20:45:17 INFO mapred.LocalDistributedCacheManager: Creating symlink: /app/hadoop/tmp/mapred/local/1454204717451/joda-time-2.9.1-no-tzdb.jar <- /usr/local/hadoop/sbin/joda-time-2.9.1-no-tzdb.jar
16/01/30 20:45:17 INFO mapred.LocalDistributedCacheManager: Localized hdfs://localhost:54310/user/hduser/lib/joda-time-2.9.1-no-tzdb.jar as file:/app/hadoop/tmp/mapred/local/1454204717451/joda-time-2.9.1-no-tzdb.jar
16/01/30 20:45:17 INFO mapred.LocalDistributedCacheManager: Creating symlink: /app/hadoop/tmp/mapred/local/1454204717452/joda-time-2.9.1.jar <- /usr/local/hadoop/sbin/joda-time-2.9.1.jar
16/01/30 20:45:17 INFO mapred.LocalDistributedCacheManager: Localized hdfs://localhost:54310/user/hduser/lib/joda-time-2.9.1.jar as file:/app/hadoop/tmp/mapred/local/1454204717452/joda-time-2.9.1.jar
16/01/30 20:45:17 INFO mapred.LocalDistributedCacheManager: file:/app/hadoop/tmp/mapred/local/1454204717451/joda-time-2.9.1-no-tzdb.jar
16/01/30 20:45:17 INFO mapred.LocalDistributedCacheManager: file:/app/hadoop/tmp/mapred/local/1454204717452/joda-time-2.9.1.jar
16/01/30 20:45:17 INFO mapreduce.Job: The url to track the job: http://localhost:8080/
16/01/30 20:45:17 INFO mapreduce.Job: Running job: job_local1787244132_0001
16/01/30 20:45:17 INFO mapred.LocalJobRunner: OutputCommitter set in config null
16/01/30 20:45:18 INFO mapred.LocalJobRunner: OutputCommitter is org.apache.hadoop.mapreduce.lib.output.FileOutputCommitter
16/01/30 20:45:18 INFO mapred.LocalJobRunner: Waiting for map tasks
16/01/30 20:45:18 INFO mapred.LocalJobRunner: Starting task: attempt_local1787244132_0001_m_000000_0
16/01/30 20:45:18 INFO mapred.Task:  Using ResourceCalculatorProcessTree : [ ]
16/01/30 20:45:18 INFO mapred.MapTask: Processing split: hdfs://localhost:54310/user/hduser/input/sentimentFeedback7.csv:0+143748596
16/01/30 20:45:18 INFO mapred.MapTask: (EQUATOR) 0 kvi 26214396(104857584)
16/01/30 20:45:18 INFO mapred.MapTask: mapreduce.task.io.sort.mb: 100
16/01/30 20:45:18 INFO mapred.MapTask: soft limit at 83886080
16/01/30 20:45:18 INFO mapred.MapTask: bufstart = 0; bufvoid = 104857600
16/01/30 20:45:18 INFO mapred.MapTask: kvstart = 26214396; length = 6553600
16/01/30 20:45:18 INFO mapred.MapTask: Map output collector class = org.apache.hadoop.mapred.MapTask$MapOutputBuffer
16/01/30 20:45:18 INFO mapred.MapTask: Starting flush of map output
16/01/30 20:45:18 INFO mapred.LocalJobRunner: Starting task: attempt_local1787244132_0001_m_000001_0
16/01/30 20:45:18 INFO mapred.Task:  Using ResourceCalculatorProcessTree : [ ]
16/01/30 20:45:18 INFO mapred.MapTask: Processing split: hdfs://localhost:54310/user/hduser/input/allergyConsumption7.csv:0+134217728
16/01/30 20:45:18 INFO mapred.MapTask: (EQUATOR) 0 kvi 26214396(104857584)
16/01/30 20:45:18 INFO mapred.MapTask: mapreduce.task.io.sort.mb: 100
16/01/30 20:45:18 INFO mapred.MapTask: soft limit at 83886080
16/01/30 20:45:18 INFO mapred.MapTask: bufstart = 0; bufvoid = 104857600
16/01/30 20:45:18 INFO mapred.MapTask: kvstart = 26214396; length = 6553600
16/01/30 20:45:18 INFO mapred.MapTask: Map output collector class = org.apache.hadoop.mapred.MapTask$MapOutputBuffer
16/01/30 20:45:18 INFO mapred.MapTask: Starting flush of map output
16/01/30 20:45:18 INFO mapred.LocalJobRunner: Starting task: attempt_local1787244132_0001_m_000002_0
16/01/30 20:45:18 INFO mapred.Task:  Using ResourceCalculatorProcessTree : [ ]
16/01/30 20:45:18 INFO mapred.MapTask: Processing split: hdfs://localhost:54310/user/hduser/input/allergyConsumption7.csv:134217728+105486421
16/01/30 20:45:18 INFO mapred.MapTask: (EQUATOR) 0 kvi 26214396(104857584)
16/01/30 20:45:18 INFO mapred.MapTask: mapreduce.task.io.sort.mb: 100
16/01/30 20:45:18 INFO mapred.MapTask: soft limit at 83886080
16/01/30 20:45:18 INFO mapred.MapTask: bufstart = 0; bufvoid = 104857600
16/01/30 20:45:18 INFO mapred.MapTask: kvstart = 26214396; length = 6553600
16/01/30 20:45:18 INFO mapred.MapTask: Map output collector class = org.apache.hadoop.mapred.MapTask$MapOutputBuffer
16/01/30 20:45:18 INFO mapred.MapTask: Starting flush of map output
16/01/30 20:45:18 INFO mapred.LocalJobRunner: map task executor complete.
16/01/30 20:45:18 WARN mapred.LocalJobRunner: job_local1787244132_0001
java.lang.Exception: java.lang.NoClassDefFoundError: org/joda/time/format/DateTimeFormat
    at org.apache.hadoop.mapred.LocalJobRunner$Job.runTasks(LocalJobRunner.java:462)
    at org.apache.hadoop.mapred.LocalJobRunner$Job.run(LocalJobRunner.java:522)
Caused by: java.lang.NoClassDefFoundError: org/joda/time/format/DateTimeFormat
    at org.peach.fooddiary.FoodDiaryMR$Map1.map(FoodDiaryMR.java:45)
    at org.peach.fooddiary.FoodDiaryMR$Map1.map(FoodDiaryMR.java:1)
    at org.apache.hadoop.mapreduce.Mapper.run(Mapper.java:145)
    at org.apache.hadoop.mapreduce.lib.input.DelegatingMapper.run(DelegatingMapper.java:55)
    at org.apache.hadoop.mapred.MapTask.runNewMapper(MapTask.java:784)
    at org.apache.hadoop.mapred.MapTask.run(MapTask.java:341)
    at org.apache.hadoop.mapred.LocalJobRunner$Job$MapTaskRunnable.run(LocalJobRunner.java:243)
    at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
    at java.util.concurrent.FutureTask.run(FutureTask.java:266)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.ClassNotFoundException: org.joda.time.format.DateTimeFormat
    at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
    ... 12 more
16/01/30 20:45:18 INFO mapreduce.Job: Job job_local1787244132_0001 running in uber mode : false
16/01/30 20:45:18 INFO mapreduce.Job:  map 0% reduce 0%
16/01/30 20:45:18 INFO mapreduce.Job: Job job_local1787244132_0001 failed with state FAILED due to: NA
16/01/30 20:45:19 INFO mapreduce.Job: Counters: 0

和子类CommissionEmployee：

public Employee(String firstName, String lastName, String socialSecurityNumber) {
    this.firstName = firstName;
    this.lastName = lastName;
    this.socialSecurityNumber = socialSecurityNumber;
}
private final String firstName;
private final String lastName;
private final String socialSecurityNumber;

public String getFirstName() {
    return firstName;
}

public String getLastName() {
    return lastName;
}

public String getSocialSecurityNumber() {
    return socialSecurityNumber;
}

我得到的同样错误是：

public CommissionEmployee(String firstName, String lastName, 
String socialSecurityNumber, double grossSales, 
double commissionRate)
{
  this.firstName = firstName;                                    
  this.lastName = lastName;                                    
  this.socialSecurityNumber = socialSecurityNumber;         
  this.grossSales = grossSales;
  this.commissionRate = commissionRate;
}

这究竟是什么意思，原因是什么，以及如何解决？

Answer 1

由于CommissionEmployee是Employee的子类，因此Java要求在构造Employee时调用CommissionEmployee的构造函数。默认情况下，这是对无参数构造函数Employee()的调用，在您的情况下不存在。

您有两种选择：

调用已存在的超类构造函数：

public CommissionEmployee(String firstName, String lastName, 
String socialSecurityNumber, double grossSales, 
double commissionRate)
{
  super(firstName, lastName, socialSecuityNumber);  
  this.grossSales = grossSales;
  this.commissionRate = commissionRate;
}

创建一个no-arg超类构造函数，并在子类构造函数中设置第一个/最后一个名称和SSN（不太理想）。超类（Employee）构造函数受到保护，因此除了子类之外不能调用它，如下所示：
```
protected Employee() {}
```

如何修复“无法应用于”错误？

1 个答案: