Question

I am making a method .equals replacing the equals method used. It accepts a object. I want it to check if that object equals the class that runs the .equals class.

I know I want to compare all the private methods I have to that object.

Is there a way to do this without making another private class to get the private variables from the object? How do I do this to compare equality not identity? I am stuck on this. Do i have to use == to compare?

Also looking online i see others use recursion. If this is the way i have to do it can you show and explain it to me?

so an example i have

public boolean equals(Object o)
{

this is in a class we will call bobtheBuilder (first thing to pop in my head)
I want to check if the object o is equal to the class.
bobTheBuilder has private object array and a private int. I assume I want to check if the array and int of this class equal the array and int of the object. First I know i need to check if it equals null so

private _arrayObject[];

private _integerBob;

public boolean equals(Object o)
{
    boolean result = true;

    if (o == null)
        result = false

    bobTheBuilder compared = (bobTheBuilder) o;

    if(compared.getArray != _arrayObject[] || compared.getInt != _integerBob)
        result == false

    return result
}

I know that equal checks for equality not identity so I assume this is wrong. How would I do this

Answer 1

Adapted from the examples in Effective Java, 2nd edition by Joshua Bloch:

public boolean equals(Object o) {
  if (o == this) {
    return true;
  }

  if (!(o instanceof BobTheBuilder)) {
    return false:
  }

  BobTheBuilder bob = (BobTheBuilder) o; //guaranteed to succeed

  return Arrays.equals(bob._arrayObject, _arrayObject)
    && bob._integerBob == _integerBob;
}

Don’t forget to override hashCode as well.

The text in the book refers to the contract set out for the equals method in Object which is here