How to use equals in java

The equals method in Java is used to compare two objects for equality. It compares the fields of two objects one by one and checks whether they are equal to determine object content equality. When overriding the equals method, you should adhere to the symmetry, reflexivity, transitivity, and consistency conventions.

equals usage in Java

In Java, the equals method is used Compares two objects for equality. It is a generic method defined by the Object class and inherited by all other classes.

Usage

equals method is usually used to compare the value content of two objects, rather than the reference Equality. It takes another object as a parameter and returns a boolean value indicating whether the two objects are equal.

Syntax:

public boolean equals(Object obj)

Parameters

• ##obj - The object to be compared

Return value

• true - if two objects are equal
• false - if two objects Not equal

Detailed explanation

When comparing two objects, the

equals method performs the following steps:

• Class equality check: First, the equals method checks whether two objects are instances of the same type. The objects are definitely not equal if they do not belong to the same class.
• Object content comparison: If the classes are equal, the equals method will compare the fields or properties of the two objects. It will compare the corresponding fields one by one and check if they are equal.
• Reference equality (optional): In some cases, the equals method may compare objects for reference equality. This means it checks if two objects point to the same memory location. They are considered equal if they point to the same memory location.

Notes

• When overriding the

  equals method, be sure to adhere to the following conventions:

  • Symmetry: For any non-null reference x and y, x.equals(y) is equal to y.equals(x).
  • Reflexivity: For any non-null reference x, x.equals(x) must be true.
  • Transitivity: For any reference x, y and z, if x.equals(y ) is true and y.equals(z) is true, then x.equals(z) must also be true.
  • Consistency: For any non-null references x and y, if they have not been modified, then x is called multiple times. equals(y) must always return the same result.
• equals methods defined for basic types (such as int, double) are final and cannot be overridden .

The above is the detailed content of How to use equals in java. For more information, please follow other related articles on the PHP Chinese website!