Eclipse & Java：使 Eclipse 在运行时也编译代码

Question

Note: I just started using Eclipse, so bear with me.

When I run a program in Eclipse, I see that it does not automatically compile the class file (using JDK 14); I have to manually run javac every time. I have "Build Automatically" checked as well. How do I make Eclipse compile the class file automatically when run?

Answer 1

Eclipse does automatically compile the class file, every time you save any sourec file.

Some things to check:

1. The java file has to be in a 'source folder'. Check this; you can right click the project, select 'properties...' and look at the build path settings, which has a section for source paths.

2. Each source path has an associated target dir. By default, this is named bin . THAT is what where your auto-compiled-on-save class files are at.

3. If all is set up properly, you can right click any java file with a 'main' method from eg the package explorer, select 'debug' from there, and see it in action. If you then make an edit to a file and save, it'll update automatically. Thus, write something like:

class Test {
    public static void main(String[] args) throws Exception {
        while (true) {
            Thread.sleep(1000L);
            System.out.println("Ping123");
        }
    }
}

run it, then edit the string literal, hit save, and you'll see the new string show up immediately, without compiling anything, without restarting anything. If that's NOT happening, you haven't properly configured the project.