多線程 調用多線程的方法 Runtime與ProcessBuilder

一般我們使用Java運行其他類中的方法的時候，無論是靜態調用還是動態調用，都是在當前的進程中執行的。也就是只有一個Java虛擬機實例在運行。有時候需要通過Java代碼啟動多個Java子進程，這樣做會消耗些資源，但是程序變得更穩定。因為新啟動的進程是在不同的虛擬機中運行的。

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在Windows中，一個虛擬機就是一個

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有兩種方式調用一個進程

1、System.exec

子進程：

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("被調用成功!");

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

主進程：

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();
        }
    }
}

調用發現在指定目錄下創建了文件，但是并沒有在控制臺輸出信息。因為TestFile子進程并沒有自己的控制臺，改進代碼

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("子進程輸出："+line);
            }
            bufferedReader.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

這里不知為何，在IDE中運行，輸出的是亂碼，在控制臺運行則不是亂碼

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既然父進程可以獲取到子進程的輸出，那么父進程如何發送消息給子進程呢？

子進程修改：

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("被調用成功!");

            BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(System.in));
            System.out.println("父進程輸入信息："+bufferedReader.readLine());

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

父進程修改：

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);
            /*向子進程輸入*/
            BufferedWriter bufferedWriter = new BufferedWriter(new OutputStreamWriter(process.getOutputStream()));
            bufferedWriter.write("Hello 子進程!");
            bufferedWriter.close();/*必須現在就關閉，否則無法向子進程輸入信息*/
            /*獲取子進程輸出*/
            BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(new BufferedInputStream(process.getInputStream())));
            String line;
            while ((line = bufferedReader.readLine())!=null){
                System.out.println("子進程輸出："+line);
            }
            bufferedReader.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

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2、使用ProcessBuilder建立子進程

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");
        /*設置工作目錄*/
        processBuilder.directory(new File("E:\\GitHub\\tools\\JavaEEDevelop\\out\\production\\Lesson1_JavaSe_Demo1"));
        Process process = processBuilder.start();

         /*向子進程輸入*/
        BufferedWriter bufferedWriter = new BufferedWriter(new OutputStreamWriter(process.getOutputStream()));
        bufferedWriter.write("Hello 子進程!");
        bufferedWriter.close();/*必須現在就關閉，否則無法向子進程輸入信息*/
            /*獲取子進程輸出*/
        BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(new BufferedInputStream(process.getInputStream())));
        String line;
        while ((line = bufferedReader.readLine())!=null){
            System.out.println("子進程輸出："+line);
        }
        bufferedReader.close();


    }
}

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