产生java.io.IOException：不能运行程序 “的Java com.alter.change.on.demand.jobs.HelloWorld2”：错误= 2，没有这样的文件或目录

Question

package com.alter.change.on.demand.jobs; 

import java.io.File; 
import java.io.IOException; 

public class HelloWorld { 

    public static void main(String args[]){ 
     for(int i = 0; i<5 ; i++){ 
      System.out.println("Helloo"); 
     } 

     Process process = null; 
     ProcessBuilder pb = new ProcessBuilder(new String[]{"java" + " " + "com.alter.change.on.demand.jobs.HelloWorld2"}); 

     try { 
      process = pb.start(); 
     } catch (IOException e) { 
      e.printStackTrace(); 
     } 
     try { 
      process.waitFor(); 
     } catch (InterruptedException e) { 
      e.printStackTrace(); 
     } 
     int exitVal = process.exitValue(); 
     System.out.println(exitVal); 
    } 
} 

和

package com.alter.change.on.demand.jobs; 
    public class HelloWorld2 { 

    public static void main(String[] args){ 
     System.out.println("Main 2..testing"); 
    } 
} 

java.io.IOException: Cannot run program "java com.alter.change.on.demand.jobs.HelloWorld2": error=2, No such file or directory

at java.lang.ProcessBuilder.start(ProcessBuilder.java:1048)

at com.alter.change.on.demand.jobs.HelloWorld.main(HelloWorld.java:22)

Caused by: java.io.IOException: error=2, No such file or directory

at java.lang.UNIXProcess.forkAndExec(Native Method)

at java.lang.UNIXProcess.(UNIXProcess.java:248)

at java.lang.ProcessImpl.start(ProcessImpl.java:134)

at java.lang.ProcessBuilder.start(ProcessBuilder.java:1029)

... 1 more

Exception in thread "main" java.lang.NullPointerException

at com.alter.change.on.demand.jobs.HelloWorld.main(HelloWorld.java:28)

Answer 1

package com.alter.change.on.demand.jobs; 

    import java.io.IOException; 

    public class HelloWorld { 

    public static void main(String args[]){ 
    for(int i = 0; i<5 ; i++){ 
    System.out.println("Helloo"); 
    } 
    Process process = null; 
    ProcessBuilder pb = new ProcessBuilder(new String[]{"java","com.alter.change.on.demand.jobs.HelloWorld2"}); 

    try { 
    process = pb.start(); 
    } catch (IOException e) { 
    e.printStackTrace(); 
    } 
    try { 
    process.waitFor(); 
    } catch (InterruptedException e) { 
    e.printStackTrace(); 
    } 
    int exitVal = process.exitValue(); 
    System.out.println(exitVal); 
    } 
    } 

---

ε-分离中的ProcessBuilder通过用逗号（，）的值工作对我来说，也确保java命令是从包含类文件的目录执行。 - 同样，当从命令行执行时，必须包括包名，后面跟类名，例如在这种情况下：java com.alter.change.on.demand.jobs.HelloWorld（请记住它是当前目录包含类文件，或者应使用-cp选项为类文件所在的目录提供路径）