Field hashCode() method in Java with Examples

The hashCode() method of java.lang.reflect.Field used to get the hashcode for this Field. Final Hashcode is computed as the exclusive-or of the hashcodes for the underlying field’s declaring class name and its name. The hashcode is always the same if the object doesn’t change. Hashcode is a unique code generated by the JVM at the time of object creation. It can be used to perform some operation on hashing related algorithm like a hashtable, hashmap etc. An object can also be searched with this unique code.

Syntax:

public int hashCode()

Parameters: This method accepts nothing.



Return value: This method returns an integer which is the hash code value for this object.

Below programs illustrate hashCode() method:
Program 1:

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// Java program to demonstrate hashCode() method
  
import java.lang.reflect.Field;
  
public class GFG {
  
    public static void main(String[] args)
        throws Exception
    {
  
        // Get the marks field object
        Field field = User.class.getField("Marks");
  
        // Apply hashCode Method on User Object
        // to get the hashCode of Marks field
        int value = field.hashCode();
  
        // print result
        System.out.println("HashCode of Marks field"
                           + " is " + value);
  
        // Now Get the Fees field object
        field = User.class.getField("Fees");
  
        // Apply hashCode Method on User Object
        // to get the hashcode of Fees field
        value = field.hashCode();
  
        // print result
        System.out.println("HashCode of Fees field"
                           + " is " + value);
  
        // Now Get the name field object
        field = User.class.getField("name");
  
        // Apply hashCode Method on User Object
        // to get the hashCode of name field
        value = field.hashCode();
  
        // print result
        System.out.println("HashCode of name field"
                           + " is " + value);
    }
}
  
// sample User class
class User {
  
    // static double values
    public static double Marks = 34.13;
    public static float Fees = 3413.99f;
    public static String name = "Aman";
  
    public static double getMarks()
    {
        return Marks;
    }
  
    public static void setMarks(double marks)
    {
        Marks = marks;
    }
  
    public static float getFees()
    {
        return Fees;
    }
  
    public static void setFees(float fees)
    {
        Fees = fees;
    }
  
    public static String getName()
    {
        return name;
    }
  
    public static void setName(String name)
    {
        User.name = name;
    }
}

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Output:

HashCode of Marks field is 71482573
HashCode of Fees field is 591398
HashCode of name field is 1779040

Program 2:

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// Java program to demonstrate hashCode() method
  
import java.lang.reflect.Field;
import java.time.Month;
  
public class GFG {
  
    public static void main(String[] args)
        throws Exception
    {
  
        // Get all field objects of Month class
        Field[] fields = Month.class.getFields();
  
        for (int i = 0; i < fields.length; i++) {
  
            // print name of Fields
            System.out.println("HashCode of Field: "
                               + fields[i].hashCode());
        }
    }
}

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Output:

HashCode of Field: -297508095
HashCode of Field: 1296412905
HashCode of Field: 1475695976
HashCode of Field: 1343692077
HashCode of Field: 1404020238
HashCode of Field: 1401709321
HashCode of Field: 1401709395
HashCode of Field: 538235208
HashCode of Field: 2125827066
HashCode of Field: -1718938229
HashCode of Field: -1007182215
HashCode of Field: 59532142

References: https://docs.oracle.com/javase/8/docs/api/java/lang/reflect/Field.html#hashCode–



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