解决Runtime.exec() 无法读取命令输出

关键：输出分2种，标准输出和错误输出，获取正确的输出流才能取到想要的结果

Runtime.exec()  在windows中执行命令的时候，在cmd中能看到输出，但是代码却读取不到，应为我们通常用标准输出流，结果就是读不到结果为null

代码一直等着。也就是为什么我们用 cmdxx 1>result.log 无结果   cmdxx 2>result.log 却能取到结果，1是标准输出  2错误输出

错误输出流例子

try {
Runtime rt = Runtime.getRuntime();
Process proc = rt.exec("javac");
InputStream stderr = proc.getErrorStream();
InputStreamReader isr = <span style="color:#ff0000;">new InputStreamReader(stderr); </span>
BufferedReader br = new BufferedReader(isr);
String line = null;
System.out.println("<ERROR>");
while ((line = br.readLine()) != null)
System.out.println(line);
System.out.println("</ERROR>");
int exitVal = proc.waitFor();
System.out.println("Process exitValue: " + exitVal);
} catch (Throwable t) {
t.printStackTrace();
} 标准输出流例子
try {
Runtime rt = Runtime.getRuntime();
Process proc = rt.exec("dir");
InputStream stdin = proc.getInputStream();
InputStreamReader isr = <span style="color:#ff0000;">new InputStreamReader(stdin); </span>
BufferedReader br = new BufferedReader(isr);
String line = null;
System.out.println("<OUTPUT>");
while ((line = br.readLine()) != null)
System.out.println(line);
System.out.println("</OUTPUT>");
int exitVal = proc.waitFor();
System.out.println("Process exitValue: " + exitVal);
} catch (Throwable t) {
t.printStackTrace();
}
参考：http://berdy.iteye.com/blog/810223