Runtime.exec()无输出

Question

运行4个“街道”进程的代码：

for (int i=0; i < NUM_STREETS; i++) {
        Process process = runtime.exec("java -classpath \\bin trafficcircle.Street 1 2");

        InputStream is = process.getInputStream();
        InputStreamReader isr = new InputStreamReader(is);
        BufferedReader br = new BufferedReader(isr);
        String line;

        while ((line = br.readLine()) != null && !line.isEmpty()) {
            System.out.println(line);
            System.out.flush();
        }

        InputStream es = process.getErrorStream();
        InputStreamReader esr = new InputStreamReader(es);
        BufferedReader br2 = new BufferedReader(esr);

        while ((line = br2.readLine()) != null && !line.isEmpty()) {
            System.out.println(line);
            System.out.flush();
        }

        int exitVal = process.waitFor();
        System.out.println("Process exitValue: " + exitVal);
    }

其中‘街道’是：

public class Street {

/**
 * @param args
 * 0 - Simulation run time
 * 1 - Flow time interval
 */
public static void main(String[] args) {
    System.out.println(args[0]);
    System.out.println(args[1]);
    System.out.flush();
}

}

打印输出：

Error: Could not find or load main class trafficcircle.Street
Process exitValue: 1
Error: Could not find or load main class trafficcircle.Street
Process exitValue: 1
Error: Could not find or load main class trafficcircle.Street
Process exitValue: 1
Error: Could not find or load main class trafficcircle.Street
Process exitValue: 1

我的Eclipse项目中的'Street.class‘位于\bin包的trafficcircle下。我以为如果找不到的话Runtime.exec会先抱怨...这是怎么回事？

Answer 1

我假设你得到了一个你正在丢弃的错误。尝试使用ProcessBuilder.redirectErrorStream(true);

当您尝试运行一个命令时，它不是在shell中运行的，并且可能会得到一个您在命令行中看不到的错误。我会显式地使用

"java","-classpath","bin","trafficcircle.Street","1","2"`

并确保您收到任何错误消息。

另一种选择是使用像这样的shell

"/bin/bash", "-c", "java -classpath bin trafficcircle.Street 1 2"

Answer 2

使用./bin (带点)来使用相对路径。