what do you mean by Shallow Cloning and Deep Cloning in java?

Problem statement: Shallow copy vs Deep copy.
shallow = little depth
Shallow copy [meaning reference copy]
is method of copying an object and is followed by default in cloning. In this method the fields of an old object X are copied to the new object Y. While copying the object type field the reference is copied to Y i.e object Y will point to same location as pointed out by X. If the field value is a primitive type it copies the value of the primitive type

Therefore, any changes made in referenced objects in object X or Y will be reflected in other object

Deep copy [meaning object copy]
If we want to create a deep copy of object X and place it in a new object Y then new copy of any referenced objects fields are created and these references are placed in object Y. This means any changes made in referenced object fields in object X or Y will be reflected only in that object and not in the other. In below example, we create a deep copy of object.

A deep copy copies all fields, and makes copies of dynamically allocated memory pointed to by the fields. A deep copy occurs when an object is copied along with the objects to which it refers.
Explanation with program:

import java.util.ArrayList;

class TestExe {

    int x, y;

}

// reference of TestExe and implements clone with deep copy

class Test2 implements Cloneable {

    int a, b;

    TestExe c = new TestExe();

    public Object clone() throws CloneNotSupportedException {

        // Assign the shallow copy to new reference variable t

        Test2 t = (Test2) super.clone();

        t.c = new TestExe();

        return t;

    }

}

public class DeepCloning {

    public static void main(String args[]) throws CloneNotSupportedException {

        Test2 t1 = new Test2();

        t1.a = 10;

        t1.b = 20;

        t1.c.x = 30;

        t1.c.y = 40;

        Test2 t2 = (Test2) t1.clone();

        t2.a = 100;

        // Change in primitive type of t2 will not be reflected in t1 field

        t2.c.x = 300;

        // Change in object type field of t2 will not be reflected in t1(deep copy)

        System.out.println(t1.a + " " + t1.b + " " + t1.c.x + " " + t1.c.y);

        System.out.println(t2.a + " " + t2.b + " " +t2.c.x + " " + t2.c.y);

    }

}
Output:
10 20 30 40
100 20 300 0