从另一个java类编译java文件

我正在尝试从另一个Java类（ExecuteShellComand.Java）编译一个Java文件（str.Java）。我试图做的是，如果“str.java”编译成功，那么我想执行“javastr”命令，但是如果编译失败，那么应该打印正确的stacktrace或错误。我正在将stacktrace或错误存储在

输出

变量中

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但是，当我执行这段代码时，尽管“str.java”中有一些错误，但System.out.println（output）并没有打印错误。

Process类试图模拟操作系统进程。这意味着，进程为错误和正常消息保留不同的输出流，为输入保留一个流。在UNIX中，应为：

import java.io.BufferedReader;
import java.io.InputStreamReader;

public class ExecuteShellComand {

    public static void main(String[] args) {

        ExecuteShellComand obj = new ExecuteShellComand();
        String className = "str.java";
        String command = "javac " + className;
        String output = obj.executeCommand(command);
        System.out.println(output);// prints the output of the executed command
    }

    private String executeCommand(String command) {
        StringBuffer output = new StringBuffer();
        Process p;
        try {
            p = Runtime.getRuntime().exec(command);
            p.waitFor();
            BufferedReader reader = new BufferedReader(new InputStreamReader(p.getInputStream()));
            String line = "";
            while ((line = reader.readLine()) != null) {
                output.append(line + "\n");
            }

        } catch (Exception e) {
            e.printStackTrace();
        }

        return output.toString();

    }

}

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如果要从命令捕获错误，则应捕获错误流而不是输入流

因此，替换

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

public class ExecuteShellComand {

    public static void main(String[] args) {
        ExecuteShellComand obj = new ExecuteShellComand();
        String className = "str.java";
        String command = "javac " + className;
        obj.executeCommand(command);
        System.out.println(obj.output);
        System.out.println(obj.errors);
    }

    private String errors;
    private String output;

    private void executeCommand(String command) {
        Process p;
        try {
            p = Runtime.getRuntime().exec(command);
            p.waitFor();
            errors = readStream(p.getErrorStream());
            output = readStream(p.getInputStream());
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    private String readStream(InputStream inputStream) throws IOException {
        StringBuffer output = new StringBuffer();
        BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream));
        String line = "";
        while ((line = reader.readLine()) != null) {
            output.append(line + "\n");
        }
        return output.toString();
    }

}

与

---

如果我必须捕获这两个流呢？然后你可以捕获InputsReal和errorstream作为不同的BufferedReader并从中获取数据。顺便说一下，由于Java 6，Java提供了一种在运行时编译类的标准方法。请在此处查看这篇文章：

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

public class ExecuteShellComand {

    public static void main(String[] args) {
        ExecuteShellComand obj = new ExecuteShellComand();
        String className = "str.java";
        String command = "javac " + className;
        obj.executeCommand(command);
        System.out.println(obj.output);
        System.out.println(obj.errors);
    }

    private String errors;
    private String output;

    private void executeCommand(String command) {
        Process p;
        try {
            p = Runtime.getRuntime().exec(command);
            p.waitFor();
            errors = readStream(p.getErrorStream());
            output = readStream(p.getInputStream());
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    private String readStream(InputStream inputStream) throws IOException {
        StringBuffer output = new StringBuffer();
        BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream));
        String line = "";
        while ((line = reader.readLine()) != null) {
            output.append(line + "\n");
        }
        return output.toString();
    }

}

BufferedReader reader = new BufferedReader(new InputStreamReader(p.getInputStream()));

BufferedReader reader = new BufferedReader(new InputStreamReader(p.getErrorStream()));