Java Objects Class Example

By Atul Rai | Last Updated: May 31, 2023 Previous       Next

The Objects utility class is part of java.util package and was introduced in Java 1.7. It provides static methods that allow developers to perform operations on objects, handle null values gracefully, and simplify common tasks such as object comparison, hash code generation, and null-safe toString() implementations.

In this blog, we will explore the various methods available in the Objects class, along with examples to demonstrate their usage.

1. equals(Object a, Object b)

The equals method compares two objects for equality and returns a Boolean value indicating whether they are equal or not. It handles null values gracefully, allowing you to compare objects even when they are null.

String str1 = "Hello";
String str2 = "Hello";
String str3 = "World";

boolean isEqual1 = Objects.equals(str1, str2);
// Output: true

boolean isEqual2 = Objects.equals(str1, str3);
// Output: false

boolean isEqual3 = Objects.equals(null, str1);
// Output: false

2. deepEquals(Object a, Object b)

The deepEquals method is similar to equals, but it performs a deep comparison of array elements and nested objects. It can handle multidimensional arrays and recursively compares the elements of the array or objects.

int[] arr1 = {1, 2, 3};
int[] arr2 = {1, 2, 3};
int[] arr3 = {3, 2, 1};

boolean isDeepEqual1 = Objects.deepEquals(arr1, arr2);
// Output: true

boolean isDeepEqual2 = Objects.deepEquals(arr1, arr3);
// Output: false

3. hashCode(Object o)

The hashCode method returns the hash code of the specified object. It handles null values and ensures that equal objects have the same hash code.

String str = "Hello";
int hashCode = Objects.hashCode(str);
System.out.println(hashCode); // Output: 69609650


// When a string is NULL
String name = null;
int hashCode1 = Objects.hashCode(name);
System.out.println(hashCode1); // Output: 0

4. toString(Object o)

The toString method returns a string representation of the specified object. If the object is null, it returns the string "null".

String str = "Hello";
String strRepresentation = Objects.toString(str);
System.out.println(strRepresentation);
// Output: Hello

String nullStr = null;
String nullStrRepresentation = Objects.toString(nullStr);
System.out.println(nullStrRepresentation);
// Output: null

5. isNull(Object obj) and nonNull(Object obj)

The isNull method checks whether the specified object is null and returns a Boolean value accordingly. Conversely, the nonNull method checks if the object is not null.

String str = "Hello";

boolean isNull = Objects.isNull(str);
// Output: false

boolean isNonNull = Objects.nonNull(str);
// Output: true

6. requireNonNull(T obj) and requireNonNull(T obj, String message)

The requireNonNull method checks if the specified object is null and throws a NullPointerException if it is. The second variant allows you to provide a custom error message.

String str = "Hello";
String nullStr = null;

Objects.requireNonNull(str);
// No exception thrown

Objects.requireNonNull(nullStr, "The object cannot be null!");
// Output: NullPointerException with the specified error message

7. compare(T a, T b, Comparator<? super T> c)

The compare method compares two objects of type T using the specified Comparator. It returns an integer value indicating the relationship between the two objects: negative if a is less than b, positive if a is greater than b, and zero if they are equal.

String str1 = "Apple";
String str2 = "Banana";

int result1 = Objects.compare(str1, str2, String.CASE_INSENSITIVE_ORDER);
// Output: a negative value since "Apple" comes before "Banana" in a case-insensitive comparison

int result2 = Objects.compare(str2, str1, String.CASE_INSENSITIVE_ORDER);
// Output: a positive value since "Banana" comes after "Apple" in a case-insensitive comparison

int result3 = Objects.compare(str1, str1, String.CASE_INSENSITIVE_ORDER);
// Output: 0 since both strings are equal in a case-insensitive comparison

The compare method is particularly useful when you need to sort or order objects based on a specific criterion provided by a Comparator.

References

1. Class Objects- JavaDoc
2. Java StringJoiner Class: Simplify String Concatenation