swapping of objects in java [duplicate]

Answer 1

What gets passed to a method is a copy of the reference of the object. So, no matter how many times you re-assign the references, the original reference will not be affected.

Try this:

static void reverse(StringBuilder builder) {
    builder.reverse();
}

public static void main(String[] args) {
    StringBuilder builder = new StringBuilder("hello");
    System.out.println(builder);
    reverse(builder);
    System.out.println(builder);
}

However, the below method wouldn't make any difference to the original object passed in.

static void swap(StringBuilder builder) {
    builder = null;
}