What does equals mean in java

In Java, the equals() method determines the equality of objects by comparing the contents of the objects, rather than the references: Default implementation: Compares whether the objects are null or whether the memory addresses are equal. Overriding methods: Compare properties to determine logical equality. Complies with reflectivity, transitivity, and consistency specifications.

Meaning of equals in Java

In Java, equals() method is used to compare two objects of equality. It determines whether two objects are logically equal without comparing their memory references.

Detailed explanation:

• Comparison logical equality: The equals() method compares the contents or status of two objects, rather than their memory addresses. It essentially determines whether they represent the same entity.
• Default implementation: The default equals() method of a class in Java checks whether the object is null, and returns true if both are null. Otherwise, it compares their memory addresses and returns true if they are equal, false otherwise.

• Override the equals() method: In order to correctly compare the equality of custom objects, you need to override the equals() method of the Object class. This overriding method should:

  • Compare the properties of two objects to determine whether they are logically equal.
  • If the objects are the same, return true; otherwise, return false.
  • Adhere to the specifications of the equals() method (including reflection and transitivity).

• Reflectivity, transitivity and consistency: The equals() method should meet the following principles:

  • Reflectivity : The object should be equal to itself (i.e. o.equals(o) is true).
  • Transitiveness: If o.equals(p) is true and p.equals(q) is true, then o.equals(q) is also true.
  • Consistency: For two non-null objects o and p, consecutive calls to o.equals(p) should always return the same boolean value.

Importance:

equals() method is crucial in Java because:

• It is used in data structures such as sets to compare and filter elements based on equality.
• It allows developers to define custom equality rules to suit the needs of a specific application.
• It helps ensure that objects are compared consistently across applications.

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