1.java进程间通信

1. Runtime+.Process可以启动新的进程

Runtime rt = Runtime.getRuntime();
Process exec = rt.exec("shutdown -a");
exec.waitFor();  //当前进程阻塞，直到调用的进程运行结束。        System.out.println("exec.exitValue()="+exec.exitValue());  //正常结束时,子进程的返回值为0

2.ProcessBuilder+Process

ProcessBuilder pb = new ProcessBuilder("javac", "-d",".","src/testExcel/D.java");
try {
    Process p = pb.start();
    p.waitFor();
    System.out.println(p.exitValue());
} catch (Exception e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
}

3.父进程获取子进程的返回值

exec2.waitFor();直到调用的进程运行结束，否则可能获取到的输出不完整。

Runtime rt = Runtime.getRuntime();
Process exec2 = rt.exec("java testExcel/D");  // 运行D.class对应的字节码文件
exec2.waitFor();
System.out.println("exec2.exitValue()="+exec2.exitValue());
OutputStream outputStream = exec2.getOutputStream();
InputStream inputStream = exec2.getInputStream();
BufferedReader reader = new BufferedReader( new InputStreamReader(inputStream));
while(reader.ready())
    System.out.println("reader.readLine()"+reader.readLine());

测试程序代码如下：

package testExcel;
public class D{
    public static void main(String[] args) {
        System.out.println("D out1");
        System.out.println("D out2");
        System.out.println("D out3");
    }
}

package child;

import java.io.*;
import java.nio.CharBuffer;
import java.util.Arrays;

public class ProcessCommunication{

    public static void main(String[] args) {
        System.out.println(System.getProperty("user.dir"));  //D:TMPEclipseInternalValClu
        File file = new File("../test.txt");
        try {
            if(!file.exists())
                file.createNewFile();  //会创建于一个文件，在D:TMPEclipse	est.txt
        } catch (IOException e2) {
            // TODO Auto-generated catch block
            e2.printStackTrace();
        }
        System.out.println(file.getAbsolutePath()); //、    
        try {
            System.out.println(file.getCanonicalPath());  //D:TMPEclipse	est.txt
        } catch (IOException e1) {
            e1.printStackTrace();
        }
        System.out.println(file.getPath());  //..	est.txt

        System.out.println();
        Runtime rt = Runtime.getRuntime();try {
//            执行一些命令，启动进程
//            Process exec = rt.exec("shutdown.exe -s -t 3000");
            Process exec = rt.exec("shutdown -a");
//            rt.exec("mstsc");  
            exec.waitFor();  //当前进程阻塞，直到调用的进程运行结束。
            System.out.println("exec.exitValue()="+exec.exitValue());  //正常结束时,子进程的返回值为0

            Process exec1 = rt.exec("javac -d . src/testExcel/D.java");  // 执行编译D.java文件的命令
            exec1.waitFor();
            System.out.println(exec1.exitValue());
            Process exec2 = rt.exec("java testExcel/D");  // 运行D.class对应的字节码文件
            exec2.waitFor();
            System.out.println("exec2.exitValue()="+exec2.exitValue());
            OutputStream outputStream = exec2.getOutputStream();
            InputStream inputStream = exec2.getInputStream();
            BufferedReader reader = new BufferedReader( new InputStreamReader(inputStream));
            while(reader.ready())
                System.out.println("reader.readLine()"+reader.readLine());
            byte[] b =new byte[100];
            inputStream.read(b);
            System.out.println("new String(b)"+new String(b,"utf-8"));
            System.out.println("查看内存");
            System.out.println(rt.freeMemory()+"	"+rt.totalMemory()+"	"+rt.maxMemory()/1024/8+"	"+rt.availableProcessors());
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        
        ProcessBuilder pb = new ProcessBuilder("javac", "-d",".","src/testExcel/D.java");
        try {
            Process p = pb.start();
            p.waitFor();
            System.out.println(p.exitValue());
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        ProcessBuilder pb2 = new ProcessBuilder("java", "testExcel/D");
        try {
            Process p2 = pb2.start();
            p2.waitFor();
            System.out.println(p2.exitValue());
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        
    }

}

D:TMPEclipseInternalValClu
D:TMPEclipseInternalValClu..	est.txt
D:TMPEclipse	est.txt
..	est.txt

exec.exitValue()=1116
0
exec2.exitValue()=0
reader.readLine()D out1
reader.readLine()D out2
reader.readLine()D out3
new String(b)