What does equal mean in java?

equal() method is used in Java to compare the equality of two objects. It returns a Boolean value indicating whether they are equal. The equal() method performs comparisons by checking object references, types, and delegation to subclasses. For custom classes, you can customize comparison rules by overriding the equal() method, following the principles of reflexivity, symmetry, transitivity, and consistency.

The role of the equal() method in Java

In Java, the equal() method is the Object class The core method, which is used to compare two objects for equality. This method returns a Boolean value indicating whether the two objects are equal.

Specific implementation

equal() method compares two objects through the following steps:

1. Check object reference: Two object references are equal if they point to the same object.
2. Check the type of the object: If two objects are not of the same type, they are not equal.
3. Delegating to subclasses: If the two objects are of the same type, this method will delegate to the subclass for further comparison.

Override the equal() method

For custom classes, you can customize the comparison rules by overriding the equal() method. The overridden equal() method should adhere to the following principles:

• Reflexivity: x.equals(x) should return true for any non-null reference value x.
• Symmetry: For any non-null reference values ​​x and y, if x.equals(y), then y.equals(x) should also return true.
• Transitiveness: For any non-null reference values ​​x, y, and z, if x.equals(y) is true, and y.equals(z) is true, then x. equals(z) should also return true.
• Consistency: For any non-null reference values ​​x and y, if the hashCode() method is called multiple times, the result of x.equals(y) should be consistent.

Example

The following is an example of a custom class that overrides the equal() method:

<code class="java">class Person {
    private String name;
    private int age;

    @Override
    public boolean equals(Object obj) {
        if (obj instanceof Person) {
            Person other = (Person) obj;
            return this.name.equals(other.name) && this.age == other.age;
        }
        return false;
    }
}</code>

In this example, equal The () method compares the name and age fields of two Person objects to determine equality.

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