Java Process.exitValue & Process.waitFor()

Process.exitValue() 采用非阻塞的方式返回，如果没有立即拿到返回值，则抛出异常

Process.waitFor() 当前线程等待，如有必要，一直要等到由该 Process 对象表示的进程已经终止。但是如果我们在调用此方法时，如果不注意的话，很容易出现主线程阻塞，Process也挂起的情况。在调用waitFor() 的时候，Process需要向主线程汇报运行状况，所以要注意清空缓存区，即InputStream和ErrorStream，在网上，很多只提到处理InputStream，忽略了ErrorStream。以下一段代码，贴出来，仅做参考。

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.List;

public class Temp implements Runnable {

    public void run() {

        String PATH_TO_SWF = "D:\\Program Files\\SWFTools\\pdf2swf.exe";
        String fromFilename = "G:\\test\\read\\suanfa.pdf";
        String saveFilename = "G:\\test\\read\\xiaoxiaoxxx.swf";

        List<String> command = new java.util.ArrayList<String>();
        command.add(PATH_TO_SWF);
        command.add("-o");
        command.add(saveFilename);
        command.add("-t");
        command.add(fromFilename);
        command.add("-s");
        command.add("languagedir=" + "G:\\test\\read\\xpdf\\chinese-simplified");

        ProcessBuilder builder = new ProcessBuilder();
        builder.command(command);

        try {
            Process convertImgProcess = builder.start();
            final InputStream is1 = convertImgProcess.getInputStream();
            final InputStream is2 = convertImgProcess.getErrorStream();
            new Thread() {
                public void run() {
                    BufferedReader br = new BufferedReader(
                            new InputStreamReader(is1));
                    try {
                        String lineB = null;

                        while ((lineB = br.readLine()) != null) {
                            if (lineB != null) System.out.println(lineB);

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

            new Thread() {
                public void run() {

                    BufferedReader br2 = new BufferedReader(
                            new InputStreamReader(is2));
                    try {

                        String lineC = null;
                        while ((lineC = br2.readLine()) != null) {

                            if (lineC != null) System.out.println(lineC);
                        }
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                }
            }.start();
            convertImgProcess.waitFor();
        } catch (Exception e) {
            System.err.println(e);
        }
    }
}