// Used with objects == is for comparing memory addresses. 
// However, it can lead to surprises when used with Strings. 
// String literals are treated in special way.
// Below each "apple" is represented by the same String object.
// This is to save memory.

class Equals {
    public static String f() {
        return "apple";
    }

    public static String g() {
        return "app";
    }
    
    public static void main(String[] args) {
        System.out.println("apple" == "apple");         // true - same String object at the same memory address
        System.out.println("apple" == f());             // true - same String object at the same memory address
        System.out.println("apple" == ("app" + "le"));  // true - compiler optimization, '+' evaluated at compile-time. Result: same as above
        System.out.println("apple" == (g() + "le"));    // false - compiler optimization does not happen. 
                                                          // Result: new String object is created for the result of + at different memory address
    }
}