Java - Class Objects Class

What is Objects Class?

Objects Class is a helper class to work with Object class.

Method

Here are some useful methods from Objects class.

Method Description
compare() compare two objects for sorting purpose. It returns 0 if both arguments are identical. Otherwise, it returns the value of c.compare(a, b). It returns 0 if both arguments are null.
deepEquals() check if two objects are deeply equal. It returns true if both arguments are deeply equal. Otherwise, it returns false. It returns true if both arguments are null.
equals() compares two objects for equality. It returns true if both arguments are equal. Otherwise, it returns false. It returns true if both arguments are null.
hash() generates a hash code for all specified objects. It can be used to compute the hash code for an object, which is based on the multiple instance fields.
hashCode() returns the hash code value of the specified object. If the argument is null, it returns 0.
isNull() returns true if the specified object is null. Otherwise, it returns false.
nonNull() performs the check opposite of what the isNull() method does.
requireNonNull(T obj) method checks if the argument is not null. If the argument is null, it throws a NullPointerException.
toString() returns a "null" string if the argument is null. For a non-null argument, it returns the value returned by calling the toString() method on the argument.

A Test Class to Demonstrate the Use of the Methods of the Objects Class

Demo

import java.time.Instant;
import java.util.Objects;
import java.util.function.Supplier;

public class Main {
  public static void main(String[] args) {
    // Compute hash code for two integers, a char, and a string
    int hash = Objects.hash(10, 8900, '\u20b9', "Hello");
    System.out.println("Hash Code is " + hash);
    // Test for equality
    boolean isEqual = Objects.equals(null, null);
    System.out.println("null is equal to null: " + isEqual);

    isEqual = Objects.equals(null, "XYZ");
    System.out.println("null is equal to XYZ: " + isEqual);
    // toString() method test
    System.out.println("toString(null) is " + Objects.toString(null));
    System.out.println("toString(null, \"XXX\") is " + Objects.toString(null, "XXX"));

    // Testing requireNonNull(T obj, String message)
    try {//from  w ww.j  a v a2s.com
      printName("abc");
      printName(null);
    } catch (NullPointerException e) {
      System.out.println(e.getMessage());
    }
    // requireNonNull(T obj, Supplier<String> messageSupplier)
    try {
      // Using a lambda expression to create a Supplier<String> object.
      // The Supplier returns a timestamped message.
      Supplier<String> messageSupplier = () -> "Name is required. Error generated on "
          + Instant.now();
      printNameWithSuplier("abc", messageSupplier);
      printNameWithSuplier(null, messageSupplier);
    } catch (NullPointerException e) {
      System.out.println(e.getMessage());
    }
  }

  public static void printName(String name) {
    // Test name for not null. Generate a NullPointerException if it is null.
    Objects.requireNonNull(name, "Name is required.");

    // Print the name if the above statement did not throw an exception
    System.out.println("Name is " + name);
  }

  public static void printNameWithSuplier(String name,
      Supplier<String> messageSupplier) {
    // Test name for not null. Generate a NullPointerException if it is null.
    Objects.requireNonNull(name, messageSupplier);

    // Print the name if the above statement did not throw an exception
    System.out.println("Name is " + name);
  }
}

Result