Java Object hashCode() Method
Java Object ClassThe Object hashCode() method is used to get the hash value of an object.
Syntax
object.hashCode()
Parameters
None 。
Return Value
Returns the object's hash value, which is an integer representing the position in the hash table.
Example
The following example demonstrates the use of the hashCode() method:
Example
class ExampleTest {
public static void main(String[] args) {
//Object using hashCode()
Object obj1 = new Object();
System.out.println(obj1.hashCode());
Object obj2 = new Object();
System.out.println(obj2.hashCode());
Object obj3 = new Object();
System.out.println(obj3.hashCode());
}
}
The output of the above program is:
225534817 1878246837 929338653
The String and ArrayList classes use the hashCode() method. Since both String and ArrayList classes inherit Object, they can directly use the hashCode() method:
Example
import java.util.ArrayList;
class ExampleTest {
public static void main(String[] args) {
//String using hashCode()
String str = new String();
System.out.println(str.hashCode()); // 0
//ArrayList using hashCode()
ArrayList<Integer> list = new ArrayList<>();
System.out.println(list.hashCode()); // 1
}
}
The output of the above program is:
0 1
The following example demonstrates that if two objects are equal, then their hash values are also equal:
Example
class ExampleTest {
public static void main(String[] args) {
//Object using hashCode()
Object obj1 = new Object();
//Assign obj1 to obj2
Object obj2 = obj1;
//Determine whether the two objects are equal
System.out.println(obj1.equals(obj2)); // true
//Get the hash values of obj1 and obj2
System.out.println(obj1.hashCode()); // 225534817
System.out.println(obj2.hashCode()); // 225534817
}
}
The output of the above program is:
true 225534817 225534817
Other Extensions