Question

There is the following code snippet:

public class Main {
    public static void main(String[] args) {
        for (int i = 0; i < 100; i++) {
            System.out.println(random());
        }
    }

    public static int random() {
        return new Random().nextInt(100);
    }
}

and we'd like to make the random() method always return the same value, not a random one.

There is Force Return action available in the debugger tool window:

but it needs to be performed manually every time we need to return a custom value. How to automate this process?

Answer

Right now there is no straightforward solution to do it right from the debugger / breakpoints view. Here is a related feature request: https://youtrack.jetbrains.com/issue/IDEA-189838

Workaround: Hardcode a needed return value and Use the HotSwap feature to control it during a program execution

• add a needed return value at the beginning of a method:

      public static int random() {
          if (true) return 1;
          return new Random().nextInt(100);
      }
  

• run the program in debug mode and observe that a new value is returned

• once it's not needed, remove the if (true) return 1; without stopping the application and perform Build | Recompile ClassName from the IntelliJ IDEA main menu