如何使用Java程序保存和打开Java程序？

Question

So I've done a little searching and Google and the StackOverflow search brings up nothing regarding this question. I thought I had found something a moment ago but it just wanted to know how to open a .exe with Java.

Anyway as the title says I would like to know how to compile and save a Java file from within a Java program and then open that same Java file I just saved.

So yeah any help with this would be greatly appreciated thanks.

EDIT:Okay what I'm talking about is to have the Java file execute.

The idea I have is using a genetic algorithm as the base and a whole lot of learning I have to yet do. Program a program that can create programs within given parameters. That would then launch itself and continue the cycle of improving itself. Basically self improving code. At the moment I have the base code of the genetic algorithm and am just trying to learn how it works as it was a tutorial I found. Yes I know it may not be possible but I like the challenge and it gives me a goal and a in my opinion fun reason to learn Java as I have attempted to before but I didn't get very far.

Anyway sorry for any confusion.

Edit2: So this is basically the code being used it has been slightly modified and messed around with though at the moment to see what I can get it to do already: http://www.theprojectspot.com/tutorial-post/creating-a-genetic-algorithm-for-beginners/3

Answer 1

您可以尝试查看http://docs.oracle.com/javase/6/docs/api/javax/tools/JavaCompiler.html 。

Answer 2

After your edit, I understood that your question is:

How can I write a java program that is clever enough to create more clever java programs?

It is going to be a difficult task. If you have the solution for the artificial intelligence that is necessary for this, then you need a technical solution for how to dynamically create a new class in runtime. I can suggest two options for that.

1. Use the java compiler API
2. Or use the javassist library.

Answer 3

You can use http://commons.apache.org/proper/commons-exec/ to start processes from Java code. You should call the same things as you would form command line. ( javac -cp... and then java -cp.. someclass )

Answer 4

import java.io.*;

public class MyProg 
{
    public static void main(String[] args) 
        throws IOException, InterruptedException
    {
        String fname = "Prog1.java";
        BufferedWriter bw;

        try{
            bw = new BufferedWriter(
                    new FileWriter(fname)
            );
        } 
        catch (IOException e) {
            System.out.println("Cannot open " + fname + "!");
            return;
        }


        final String NL = System.getProperty("line.separator");

        bw.write("public class Prog1{" + NL
                + "\tpublic static void main(String[] args) {" + NL
                + "\t\tSystem.out.println(\"hello world\");" + NL
                + "\t}" + NL
                + "}" + NL
        );
        bw.close();

        BufferedReader br;
        try {
            br = new BufferedReader(
                    new FileReader(fname)
            );
        }
        catch (FileNotFoundException e) {
            System.out.println(fname + " not found!");
            return;
        }

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





        Process p1 = new ProcessBuilder(
            "javac", "Prog1.java"
        ).start();

        int error = p1.waitFor();
        System.out.println("p1: " + error);

        /*
        Process p2 = new ProcessBuilder(
            "java", "-cp . Prog1"
        ).start();

        error = p2.waitFor();

        System.out.println("p2: " + error);
        */

        FileInputStream fin;
        try {
            fin = new FileInputStream(fname);
        }
        catch (FileNotFoundException e) {
            System.out.println(fname + " not found!");
            return;
        }

        int abyte;
        while((abyte = fin.read()) != -1)
        {
            System.out.println(abyte);
        }

        fin.close();


    }
} 


--output:--
public class Prog1{
    public static void main(String[] args) {
        System.out.println("hello world");
    }
}
p1: 0
112
117
98
108
105
99
...
...
125
10