Profiling String Comparison vs. Class.isAssignableFrom(...) Comparison.

output.txt

String comparison: 5 ms
Class comparison with isAssignableFrom: 1052 ms

Scratch.java

import java.util.Collection;
import java.util.List;
import java.util.Scanner;

public final class Scratch {

    public static final String CORRECT_CLASS_NAME = List.class.getCanonicalName();

    public static final String INCORRECT_CLASS_NAME = Scanner.class.getCanonicalName();

    public static final int TIMES = 1000000;

    public static long profileStringComp() {
        final long startMillis = System.currentTimeMillis();

        for (int i = 0; i < TIMES; i++) {
            CORRECT_CLASS_NAME.equals(CORRECT_CLASS_NAME);
            INCORRECT_CLASS_NAME.equals(CORRECT_CLASS_NAME);
        }

        return System.currentTimeMillis() - startMillis;
    }

    public static long profileAssignableFromComp() throws ClassNotFoundException {
        final long startMillis = System.currentTimeMillis();

        for (int i = 0; i < TIMES; i++) {
            Collection.class.isAssignableFrom(Class.forName(CORRECT_CLASS_NAME));
            Collection.class.isAssignableFrom(Class.forName(INCORRECT_CLASS_NAME));
        }

        return System.currentTimeMillis() - startMillis;
    }

    public static void main(final String[] args) throws Exception {
        System.out.printf("String comparison: %d ms\n", profileStringComp());
        System.out.printf("Class comparison with isAssignableFrom: %d ms\n",
                profileAssignableFromComp());
    }
}