#Use of ==

1 messages · Page 1 of 1 (latest)

tawdry sable
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So for primitives using == will work as expected because it holds values so it will compare the values but for reference types it compares to see if the objects are the same objects which is why we need to use equals? Just want to make sure I’m understanding

uneven trellisBOT
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<@&987246399047479336> please have a look, thanks.

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TJ-Bot
So for primitives using == will work as expected because it holds values so it will compare the values but for reference types it compares to see if the objects are the same objects which is why we need to use equals? Just want to make sure I’m understandi

You’ve got the core idea right!

  • For primitives, == compares the actual values (e.g., int a = 5; int b = 5; a == b is true).
  • For reference types like objects, == checks if two references point to the exact same memory location (same object), not if their internal data is equal.

That’s why for objects, you generally use .equals() to check logical equivalence (like two different String objects containing the same characters).

This distinction is key in Java’s memory model and object handling. Using == for objects often leads to subtle bugs if you meant to compare their contents rather than identities.

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keen abyss
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thus == still compares the value even for reference types

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just that the value isnt the object itself

scenic burrow
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normally ud compare properties in it

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example:

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class Person {
  @Override
  public boolean equals(Object o) {
    if (o == null || !(o instanceof Person)) { return false; }
    Person other = (Person) o;

    return name.equals(other.name) && age == other.age;
  }
}
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but its totally up to u what u want to compare

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maybe persons are identified only by their name, then age plays no role

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return name.equals(other.name);

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totally up to u what logic makes the most sense in order to compare objects with each other

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java wont do any guessing for u in terms of "oh, lemme compare property by property"

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u define the logic in ur equals method urself

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== in contrast doesnt do any of that. its built-in "magic" that simply compares the object identity

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people often say "its the objects memory address". that isnt really true but it might help understand what identity means

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another example are twins

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Person first = new Person("John");
Person second = new Person("John");
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first == second nope, false

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two different object identities

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but sure, they look alike so first.equals(second) would probably be true (provided thats how u implemented the equals method)

tawdry sable
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By default equals works like == for references right

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Unless you implement your own override for the class

scenic burrow
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and in there, the code looks like this:

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class Object {
  ...
  public boolean equals(Object o) {
    return this == o;
  }
}
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so thats the default behavior u get

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so again, "no magic". just normal java inheritance with normal java code

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