java - 在java中写入.java文件并运行脚本

Question

我目前正在尝试用 Java 编写一个 .java 文件。我有一些类 Driver 调用我的子类 Eval:

public class Driver
{
    public static void main(String[] args)
    {
        Eval eval = new Eval();
        eval.evaluate("System.out.println(\"Hello!!! I'm an auto-generated .java file!);\");
    }
}

这是我的 Eval 类(存储在同一项目中):

public class Eval
{
    public Eval()
    {

    }

    public void evaluate(String toEval)
    {
        PrintWriter writer = new PrintWriter("Auto.java", "UTF-8");
        writer.println("public class Auto");
        writer.println("{");
        writer.println("    public static void main(String[] args)");
        writer.println("    {");
        writer.println("        " + toEval;
        writer.println("    }");
        writer.println("}");
        writer.close();
    }
}

因此，我在同一目录中手动创建 Auto.java 类。我运行脚本，查看 Auto.java，令我惊讶的是，什么也没有写!

public Auto
{
}

(这就是我手动创建它后留下的方式)
如有任何建议，我们将不胜感激。
谢谢!

附注此外(尽管上述错误优先于这个问题)，我如何从 Eval 类运行这个程序？

Answer 1

试试这个:

 /**
 * @author Rustam
 */
public class Test {


    public static void main(String[] args) throws FileNotFoundException,
            UnsupportedEncodingException {

        Eval eval = new Eval();
        eval.evaluate("System.out.println(\"Hello!!! I'm an auto-generated .java file!\")");
        try {
            runProcess("javac Auto.java");
            runProcess("java Auto");
        } catch (Exception e) {
            e.printStackTrace();
        }

    }

    private static void runProcess(String command) throws Exception {
        Process pro = Runtime.getRuntime().exec(command);
        printLines(command + " stdout:", pro.getInputStream());
        printLines(command + " stderr:", pro.getErrorStream());
        pro.waitFor();
        System.out.println(command + " exitValue() " + pro.exitValue());
    }

    private static void printLines(String name, InputStream ins) throws Exception {
        String line = null;
        BufferedReader in = new BufferedReader(
                new InputStreamReader(ins));
        while ((line = in.readLine()) != null) {
            System.out.println(name + " " + line);
        }
    }
}

class Eval
{
    public Eval()
    {

    }

    public void evaluate(String toEval) throws FileNotFoundException, UnsupportedEncodingException
    {
        PrintWriter writer = new PrintWriter("Auto.java", "UTF-8");
        writer.println("public class Auto");
        writer.println("{");
        writer.println("    public static void main(String[] args)");
        writer.println("    {");
        writer.println("        " + toEval + ";");
        writer.println("    }");
        writer.println("}");
        writer.close();
        System.out.println("Auto.java created..");
    }
}

输出:

Auto.java created..
javac Auto.java exitValue() 0
java Auto stdout: Hello!!! I'm an auto-generated .java file!
java Auto exitValue() 0