关于Runtime.getRuntime()

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

public class ProcessTest {
    public static void main(String[] args) {

        try {
            String cmd = null;
            cmd = "cmd.exe /c dir";         //可以输出
            cmd = "cmd.exe /c java";    //可以输出
            cmd = "cmd.exe /c java -version 2>&1";   //可以输出
            cmd = "cmd.exe /c java -version";   //不可以输出
            
            Process process = Runtime.getRuntime().exec(cmd);
            PrintWriter writer = new PrintWriter(process.getOutputStream());
            new CommandThread(writer).start();
            BufferedReader br = new BufferedReader(new InputStreamReader(process.getInputStream()));
            
            String s = null;
            while ((s = br.readLine()) != null) {
                System.out.println(s);
            }
            Thread.currentThread().interrupt();
        } catch (Exception e) {
            e.printStackTrace();
        }

    }
    
    static class CommandThread extends Thread{
        PrintWriter writer;
        BufferedReader br = null;
        CommandThread(PrintWriter writer){
            this.writer = writer;
            br = new BufferedReader(new InputStreamReader(System.in));
            this.setDaemon(true);
        }
        
        @Override
        public void run() {
            try {
                String cmd = null;
                while((cmd = br.readLine()) != null){
                    writer.println(cmd);
                    writer.flush();
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}