java_string_compair.java

package org.example;

public class Main {
    public static void main(String[] args) {
        var sb = new StringBuilder();
        for(int i=0;i<10000000;i++){
            sb.append("a");
        }

        var base = new String(sb);
        var aaaaa = base + "a";
        var aaaab = base + "b";
        var baaaa = "b" + base;

        long dummy = 0;

        // "aaa...aaa" v.s. "aaa...aab"
        {
            long startTime = System.currentTimeMillis();
            for(int i=0;i<1000;i++) {
                if (aaaaa.equals(aaaab)) {
                    dummy += 1;
                }
            }
            long endTime = System.currentTimeMillis();
            System.out.println(endTime - startTime); // => 2901
        }

        // "aaa...aaa" v.s. "baa...aaa"
        {
            long startTime = System.currentTimeMillis();
            for(int i=0;i<1000;i++) {
                if(aaaaa.equals(baaaa)){
                    dummy += 1;
                }
            }
            long endTime = System.currentTimeMillis();
            System.out.println(endTime - startTime); // => 0
        }
    }
}