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Java Java Data Structures Organizing Data Interfaces

Posted by Jorge Otero
Jorge Otero
16,380 Points

Why he use `equals(other)` instead `obj.equals(other)`? when is appropriate to use it this way?

I would like to know the difference between equals(other) and obj.equals(other).

public int compareTo(Object obj){ 
    Treet other = (Treet) obj; 
    if(equals(other)) {
        return 0;
    }
}

1 Answer

Samuel Ferree
Samuel Ferree
31,722 Points
Samuel Ferree
Samuel Ferree
31,722 Points

If you're inside an instance method of an object, You can call it's instance method either by themselves, or prefixed with this

See below

public class Foo {
  private Bar bar;

  // In this method, we are *inside* an instance of Foo, so we can call instance methods
  // 'this', refers to the instance we are in, so it can also be used to call instance methods
  public void printYesIfEqual(Foo that) {
    if(equals(that)) {
      System.out.println("Yes!");
    }
    if(this.equals(that)) {
      System.out.println("Yes!");
    }
  }

  // In this method, we are *inside an instance of Foo, so we have access to it's 'bar' field
  // we are not however, *inside* of Bar, so to call instance methods of Bar, on our bar field
  // we need to use the '.' operator,
  // Like before, we can also access our bar field with 'this' to refer to the object that we are *inside*
  public void printYesIfSameBar(Bar otherBar) {
    if(bar.equals(otherBar)) {
      System.out.println("Yes!");
    }
    if(this.bar.equals(otherBar)) {
      System.out.println("Yes!");
    }
}
Jorge Otero
Jorge Otero
16,380 Points

That solve my problem, thanks.