Java：使用我自己的.equals将该类与该类中的另一个进行比较

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

So, you have a private array X and an int Y in a class Z.

Now, for checking the equality and not indentity,

1. First thing you should have setters and getters that will set and return the value of the private variables, eg

public void setArrayX(Object[] arr), public Object[] getArrayX()

2.now, the eqauls method would look like,

boolean equals(Object o) {
  if(Arrays.equals(this.getArrayX(),o.getArrayX()) && this.getIntY() == o.getIntY())
   return true;
  return false;
}

Answer 2

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

Answer 3

I think the best way to check the class is through the

someObject.getClass().isInstance(anotherObject)

command.

This works with inheritance as well.