java陷阱-------用java 打开一个 .exe文件

[code]
public class Test {
public static void main(String[] args) {
Runtime rt = Runtime.getRuntime();
try {
Process proc = rt.exec("C:\\Program Files\\Internet Explorer\\iexplore.exe");
int exitVal = proc.exitValue();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}

但是这样允许会出现一个异常：
Exception in thread "Main Thread" java.lang.IllegalThreadStateException: process has not exited
问题原因：
因为程序还没有退出，所以proc.exitValue();程序退出的值当然没有啦。。

怎么改呢。。。

public class Test {
public static void main(String[] args) {
Runtime rt = Runtime.getRuntime();
try {
Process proc = rt.exec("C:\\Program Files\\Internet Explorer\\iexplore.exe");
int exitVal = proc.waitFor();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}

这里主要是要学习用运行时对象来执行外面的程序。。。

下面换成javac试试
public class Test {
public static void main(String[] args) {
Runtime rt = Runtime.getRuntime();
int exitVal = 0;
try {
Process proc = rt.exec("javac");
exitVal = proc.waitFor();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
System.out.println(exitVal);
}
}

允许后发现javac死在这里了，因为proc.waitFor一直在等待关闭，而现在javac这样调用的语法有问题，所以这个程序会先输出错误信息再输出退出的val，但是这时候它想输出错误信息都输不出来，所以程序一直挂在这里。。。改的方法就是让错误信息先输出来呀~~~~~~~

public class Test {
public static void main(String[] args) {
Runtime rt = Runtime.getRuntime();
int exitVal = 0;
try {
Process proc = rt.exec("javac");
exitVal = proc.waitFor();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
System.out.println(exitVal);
}
}
//我改

public class Test {
public static void main(String[] args) {
Runtime rt = Runtime.getRuntime();
int exitVal = 0;
try {
Process proc = rt.exec("javac");
InputStream es = proc.getErrorStream();
InputStreamReader reader = new InputStreamReader(es);
BufferedReader br = new BufferedReader(reader);
StringBuffer sb = new StringBuffer();
String l = "";
while((l = br.readLine()) != null){
sb.append(l+"\n");
}
System.out.println(sb.toString());
exitVal = proc.waitFor();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
System.out.println(exitVal);
}
}


* 永远要在调用waitFor()方法之前读取数据流
* 永远要先从标准错误流中读取，然后再读取标准输出流

于是将waitFor()方法放在读取数据流后调用，目前没有发现什么问题。


正好解决了我心中的疑问，非常感谢！

我们的程序一开始就是exec完了接着waitFor()，但bat文件执行不完整：

Process proc = Runtime.getRuntime().exec(cmd);
proc.waitFor();

后面的build中在waitFor()之前读取了数据流，bat文件就可以完整执行了：

Process proc = Runtime.getRuntime().exec(cmd);
StreamGobbler errorGobbler = new StreamGobbler(proc.getErrorStream(), "Error");
StreamGobbler outputGobbler = new StreamGobbler(proc.getInputStream(), "Output");
errorGobbler.start();
outputGobbler.start();

proc.waitFor();

class StreamGobbler extends Thread {
InputStream is;

String type;

StreamGobbler(InputStream is, String type) {
this.is = is;
this.type = type;
}

public void run() {
try {
InputStreamReader isr = new InputStreamReader(is);
BufferedReader br = new BufferedReader(isr);
String line = null;
while ((line = br.readLine()) != null) {
if (type.equals("Error"))
LogManager.logError(line);
else
LogManager.logDebug(line);
}
} catch (IOException ioe) {
ioe.printStackTrace();
}
}
}


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