Java Runtime Compiling within scope

Question

Is it possible to recompile java code within a class at runtime?

Example:

package com.main;

public class Main {

public static int a = 5;
public static int b = 10;

public static void main(String[] args) {
    int c = func(a, b);

    compile("int func(int a, int b) { return a * b; }");

    int d = func(a, b); 
}

static int func(int a, int b) {
    return a + b;
}
}

So in this example the compile function would overwrite an existing method.

My program takes in marks/points which the uni gives to their students and since most subjects have a different method for calculating the overall gained scores the user should be able to change those individually.

Is it possible to do something like this without using an AST(abstract syntax tree) or having to compile a new class file which has to inherit certain methods?