java - 如果运行时打印错误则停止程序

Question

import java.lang.Process;        
import java.io.*;       
import java.io.InuputStream;       
import java.io.IOException;

 public class newsmail{    
 public static void main(String[] args) throws IOException{    
    String command = "java Newsworthy_RB";    
    Process child = Runtime.getRuntime.exec(command);  
            int c;  
    InputStream in = child.getInputStream();
    while((c=in.read())!=-1){
        System.out.print((char)c);
    }
    in.close();

    command = "java Newsworthy_CA";
    Process child = Runtime.getRuntime.exec(command);
    InputStream in = child.getInputStream();
    while((c=in.read())!=-1){
        System.out.print((char)c);
    }
    in.close();
  }

我正在一个接一个地执行两个java程序，如上面的代码所示。如果第一个程序(Newsworthy_RB)中发生任何错误，我的程序应该终止显示错误。相反，它继续执行第二个程序(Newsworthy_CA)。

应该如何获取错误流...请建议...

Answer 1

您可以通过显式调用System.exit(status)来停止程序。如果出现错误，状态应为 != 0 来指示。

您可以通过child.getErrorStream()访问错误流。

编辑:实际答案取决于您真正想要做什么。如果您的目的只是检查第一个程序是否成功终止(结束)，您可以编写以下内容:

public static void main(String[] args) throws Exception {
     Process child1 = Runtime.getRuntime().exec("cmd");
     int status1 = child1.waitFor();

     System.out.println("Exit status of child one: " + status1);

     // Something has gone wrong
     if (status1 != 0) {
         // end program
         return;
     }

     Process child2 = Runtime.getRuntime().exec("cmd2");
     int status2 = child2.waitFor();

     System.out.println("Exit status of child two: " + status2);
}

Process#waitFor() 执行以下操作(从 javadoc 复制):

causes the current thread to wait, if necessary, until the process represented by this Process object has terminated. This method returns immediately if the subprocess has already terminated. If the subprocess has not yet terminated, the calling thread will be blocked until the subprocess exits.