string-concatenation-vs-stringbuilder-vs-string-format-performance

 https://kylewbanks.com/blog/java-string-concatenation-vs-stringbuilder-vs-string-format-performance

public class TestStrings {

    private static final String PROFILE_PICTURE_URL_BASE = "https://cdn.myapp.com/user/";
    private static final String PROFILE_PICTURE_URL_EXTENSION = ".png";
    private static final String PROFILE_PICTURE_URL = "https://cdn.myapp.com/user/%d.png";

    private static final int NUM_ITERATIONS = 1000000;
    
    public static void main(String[] args) {
        int userId;
        long startTime;
        
        // String Concatentation
        startTime = System.currentTimeMillis();
        for (userId = 0; userId < NUM_ITERATIONS; userId ++) {
            String profilePictureUrl = PROFILE_PICTURE_URL_BASE + userId + PROFILE_PICTURE_URL_EXTENSION;
        }
        System.out.println("String Concatentation: " + (System.currentTimeMillis() - startTime) + "ms");
        
        // StringBuilder
        startTime = System.currentTimeMillis();
        for (userId = 0; userId < NUM_ITERATIONS; userId ++) {
            StringBuilder sb = new StringBuilder(PROFILE_PICTURE_URL_BASE);
            sb.append(userId);
            sb.append(PROFILE_PICTURE_URL_EXTENSION);
            
            String profilePictureUrl = sb.toString();
        }
        System.out.println("StringBuilder: " + (System.currentTimeMillis() - startTime) + "ms");
        
        // String.format
        startTime = System.currentTimeMillis();
        for (userId = 0; userId < NUM_ITERATIONS; userId ++) {
            String profilePictureUrl = String.format(PROFILE_PICTURE_URL, userId);
        }
        System.out.println("String.format: " + (System.currentTimeMillis() - startTime) + "ms");
    }
}