Java constant pool removal at runtime

Question

I have the following Java class:

public class Test {

    public static void main(String[] args) {
        if (false) {
            log("String_to_be_never_printed_1");
        }

        if (isPrintable()) {
            log("String_to_be_never_printed_2");
        }

    }

    private static boolean isPrintable() {
        return false;
    }

    private static void log(String s) {
        System.out.println(s);
    }

}

In both if statements, the result will be false. When I output the constant pool table for this class, I get:

Constant pool:
   #1 = Class              #2             // Test
   #2 = Utf8               Test
   ....
  #18 = Utf8               isPrintable
  #19 = Utf8               ()Z
  #20 = String             #21            // String_to_be_never_printed_2
  #21 = Utf8               String_to_be_never_printed_2
  #22 = Methodref          #1.#23         // Test.log:(Ljava/lang/String;)V
  #23 = NameAndType        #24:#25        // log:(Ljava/lang/String;)V
  ...

The String_to_be_never_printed_2 is present (#20), when String_to_be_never_printed_1 is nowhere to be seen. This is expected as the compiler optimized the first if statement.

My question is whether the VM will manage to remove the String_to_be_never_printed_2 from the constant pool (as this will never be used)?

Answer 1

Nothing is ever removed from the constants pool. There would be no purpose in this anyway, as removal would have no effect on actual memory size