Runtime.exec（）没有输出

Question

Code that runs 4 'Street' processes:

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);
    }

Where 'Street' is:

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();
}

}

Prints out:

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

'Street.class' in my Eclipse project is under \\bin in package trafficcircle. I thought Runtime.exec would complain first if it wasn't found...what's up with this?

Answer 1

I assume you are getting an error which you are discarding. Try using ProcessBuilder.redirectErrorStream(true);

When you try to run a command it is not run in a shell, and may be getting an error which you don't see on the command line. I would explicitly use

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

and make sure you are getting any error messages.

another option is to use a shell like

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

Answer 2

使用./bin（带点）来使用相对路径。