多线程 调用多线程的方法 Runtime与ProcessBuilder

一般我们使用Java运行其他类中的方法的时候，无论是静态调用还是动态调用，都是在当前的进程中执行的。也就是只有一个Java虚拟机实例在运行。有时候需要通过Java代码启动多个Java子进程，这样做会消耗些资源，但是程序变得更稳定。因为新启动的进程是在不同的虚拟机中运行的。

在Windows中，一个虚拟机就是一个

---

有两种方式调用一个进程

1、System.exec

子进程：

 package org.zln.thread;

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

 /**
  * Created by coolkid on 2015/6/21 0021.
  */
 public class TestFile {
     public static void main(String[] args)  {
         try {
             File file = new File("D:\\my.txt");
             file.createNewFile();
             System.out.println("被调用成功!");

         } catch (IOException e) {
             e.printStackTrace();
         }
     }
 }

E:\GitHub\tools\JavaEEDevelop\Lesson1_JavaSe_Demo1\src\org\zln\thread\TestFile.java

主进程：

 package org.zln.thread;

 import java.io.IOException;

 /**
  * Created by coolkid on 2015/6/21 0021.
  */
 public class TestRuntime {
     public static void main(String[] args) {
         String rootPath = "E:\\GitHub\\tools\\JavaEEDevelop\\out\\production\\Lesson1_JavaSe_Demo1";
         String mainPath = "org.zln.thread.TestFile";
         String command = "java -classpath "+rootPath+" "+mainPath;
         Runtime runtime = Runtime.getRuntime();
         try {
             System.out.println(command);
             runtime.exec(command);

         } catch (IOException e) {
             e.printStackTrace();
         }
     }
 }

E:\GitHub\tools\JavaEEDevelop\Lesson1_JavaSe_Demo1\src\org\zln\thread\TestRuntime.java

调用发现在指定目录下创建了文件，但是并没有在控制台输出信息。因为TestFile子进程并没有自己的控制台，改进代码

 package org.zln.thread;

 import java.io.*;

 /**
  * Created by coolkid on 2015/6/21 0021.
  */
 public class TestRuntime {
     public static void main(String[] args) {
         String rootPath = "E:\\GitHub\\tools\\JavaEEDevelop\\out\\production\\Lesson1_JavaSe_Demo1";
         String mainPath = "org.zln.thread.TestFile";
         String command = "java -classpath "+rootPath+" "+mainPath;
         Runtime runtime = Runtime.getRuntime();
         try {
             System.out.println(command);
             Process process = runtime.exec(command);
             BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(new BufferedInputStream(process.getInputStream())));
             String line;
             while ((line = bufferedReader.readLine())!=null){
                 System.out.println("子进程输出："+line);
             }
             bufferedReader.close();
         } catch (IOException e) {
             e.printStackTrace();
         }
     }
 }

E:\GitHub\tools\JavaEEDevelop\Lesson1_JavaSe_Demo1\src\org\zln\thread\TestRuntime.java

这里不知为何，在IDE中运行，输出的是乱码，在控制台运行则不是乱码

既然父进程可以获取到子进程的输出，那么父进程如何发送消息给子进程呢？

子进程修改：

 package org.zln.thread;

 import java.io.BufferedReader;
 import java.io.File;
 import java.io.IOException;
 import java.io.InputStreamReader;

 /**
  * Created by coolkid on 2015/6/21 0021.
  */
 public class TestFile {
     public static void main(String[] args)  {
         try {
             File file = new File("D:\\my.txt");
             file.createNewFile();
             System.out.println("被调用成功!");

             BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(System.in));
             System.out.println("父进程输入信息："+bufferedReader.readLine());

         } catch (IOException e) {
             e.printStackTrace();
         }
     }
 }

E:\GitHub\tools\JavaEEDevelop\Lesson1_JavaSe_Demo1\src\org\zln\thread\TestFile.java

父进程修改：

 package org.zln.thread;

 import java.io.*;

 /**
  * Created by coolkid on 2015/6/21 0021.
  */
 public class TestRuntime {
     public static void main(String[] args) {
         String rootPath = "E:\\GitHub\\tools\\JavaEEDevelop\\out\\production\\Lesson1_JavaSe_Demo1";
         String mainPath = "org.zln.thread.TestFile";
         String command = "java -classpath "+rootPath+" "+mainPath;
         Runtime runtime = Runtime.getRuntime();
         try {
             System.out.println(command);
             Process process = runtime.exec(command);
             /*向子进程输入*/
             BufferedWriter bufferedWriter = new BufferedWriter(new OutputStreamWriter(process.getOutputStream()));
             bufferedWriter.write("Hello 子进程!");
             bufferedWriter.close();/*必须现在就关闭，否则无法向子进程输入信息*/
             /*获取子进程输出*/
             BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(new BufferedInputStream(process.getInputStream())));
             String line;
             while ((line = bufferedReader.readLine())!=null){
                 System.out.println("子进程输出："+line);
             }
             bufferedReader.close();
         } catch (IOException e) {
             e.printStackTrace();
         }
     }
 }

E:\GitHub\tools\JavaEEDevelop\Lesson1_JavaSe_Demo1\src\org\zln\thread\TestRuntime.java

---

2、使用ProcessBuilder建立子进程

 package org.zln.thread;

 import java.io.*;

 /**
  * Created by coolkid on 2015/6/21 0021.
  */
 public class TestProcessBuilder {
     public static void main(String[] args) throws IOException {
         ProcessBuilder processBuilder = new ProcessBuilder("java","org.zln.thread.TestFile");
         /*设置工作目录*/
         processBuilder.directory(new File("E:\\GitHub\\tools\\JavaEEDevelop\\out\\production\\Lesson1_JavaSe_Demo1"));
         Process process = processBuilder.start();

          /*向子进程输入*/
         BufferedWriter bufferedWriter = new BufferedWriter(new OutputStreamWriter(process.getOutputStream()));
         bufferedWriter.write("Hello 子进程!");
         bufferedWriter.close();/*必须现在就关闭，否则无法向子进程输入信息*/
             /*获取子进程输出*/
         BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(new BufferedInputStream(process.getInputStream())));
         String line;
         while ((line = bufferedReader.readLine())!=null){
             System.out.println("子进程输出："+line);
         }
         bufferedReader.close();

     }
 }

E:\GitHub\tools\JavaEEDevelop\Lesson1_JavaSe_Demo1\src\org\zln\thread\TestProcessBuilder.java