Difference between == and .equals in Java.

Question

I know this has been covered but I\'ve seen inconsistent arguments here on SO.

So if I have:

String a = \"apple2e\";
String b = \"apple2e\";

System.         


        

Answer 1

If you change to the following: System.out.println("a==b? " + (a == b));

You get a==b? true

Whats happening here is that a and b both point to an internal cache of Strings that is maintained by the String class.

Here is the implementation of String.equals()

public boolean equals(Object anObject) {
if (this == anObject) {
    return true;
}
if (anObject instanceof String) {
    String anotherString = (String)anObject;
    int n = count;
    if (n == anotherString.count) {
    char v1[] = value;
    char v2[] = anotherString.value;
    int i = offset;
    int j = anotherString.offset;
    while (n-- != 0) {
        if (v1[i++] != v2[j++])
        return false;
    }
    return true;
    }
}
return false;
}

anObject must be a String in order to return true, if it is a reference to the same Object, then it returns true immediately. Otherwise as you can see, is is doing a character by character comparison.