TreeMap clone() Method in Java with Examples

The clone() method in Java creates a shallow copy of the TreeMap object. It means that the new TreeMap object will have the same key-value pairs as the original TreeMap object, but any changes made to the values of the new TreeMap object will not affect the original TreeMap object.

Syntax:

public Object clone()

Example 1: Using clone() method to create a shallow copy of a TreeMap object

import java.util.TreeMap;

public class TreeMapCloneExample {
    public static void main(String[] args) {
        // Creating a TreeMap object
        TreeMap<Integer, String> originalTreeMap = new TreeMap<>();
        originalTreeMap.put(1, "One");
        originalTreeMap.put(2, "Two");
        originalTreeMap.put(3, "Three");
        originalTreeMap.put(4, "Four");
        originalTreeMap.put(5, "Five");

        // Creating a shallow copy of the original TreeMap object
        TreeMap<Integer, String> clonedTreeMap = (TreeMap<Integer, String>) originalTreeMap.clone();

        // Displaying the original TreeMap object
        System.out.println("Original TreeMap: " + originalTreeMap);

        // Displaying the cloned TreeMap object
        System.out.println("Cloned TreeMap: " + clonedTreeMap);

        // Modifying the cloned TreeMap object
        clonedTreeMap.put(6, "Six");

        // Displaying the original TreeMap object after modifying the cloned TreeMap object
        System.out.println("Original TreeMap after modifying the cloned TreeMap: " + originalTreeMap);

        // Displaying the cloned TreeMap object after modifying it
        System.out.println("Cloned TreeMap after modifying it: " + clonedTreeMap);
    }
}

Output:

Original TreeMap: {1=One, 2=Two, 3=Three, 4=Four, 5=Five}
Cloned TreeMap: {1=One, 2=Two, 3=Three, 4=Four, 5=Five}
Original TreeMap after modifying the cloned TreeMap: {1=One, 2=Two, 3=Three, 4=Four, 5=Five}
Cloned TreeMap after modifying it: {1=One, 2=Two, 3=Three, 4=Four, 5=Five, 6=Six}

In the above example, we have created a TreeMap object originalTreeMap and added some key-value pairs to it. Then, we have created a shallow copy of the originalTreeMap object using the clone() method and stored it in clonedTreeMap. We have displayed both the original and cloned TreeMap objects. Then, we have modified the clonedTreeMap object by adding a new key-value pair to it. Finally, we have displayed both the original and cloned TreeMap objects again to show that modifying the cloned TreeMap object does not affect the original TreeMap object.

Example 2: Using clone() method to create a shallow copy of a TreeMap object with custom objects as values

import java.util.TreeMap;

class Employee {
    private int id;
    private String name;

    public Employee(int id, String name) {
        this.id = id;
        this.name = name;
    }

    public int getId() {
        return id;
    }

    public String getName() {
        return name;
    }

    @Override
    public String toString() {
        return "Employee{" +
                "id=" + id +
                ", name='" + name + '\'' +
                '}';
    }
}

public class TreeMapCloneExample {
    public static void main(String[] args) {
        // Creating a TreeMap object with custom objects as values
        TreeMap<Integer, Employee> originalTreeMap = new TreeMap<>();
        originalTreeMap.put(1, new Employee(101, "John"));
        originalTreeMap.put(2, new Employee(102, "Mary"));
        originalTreeMap.put(3, new Employee(103, "Bob"));

        // Creating a shallow copy of the original TreeMap object
        TreeMap<Integer, Employee> clonedTreeMap = (TreeMap<Integer, Employee>) originalTreeMap.clone();

        // Displaying the original TreeMap object
        System.out.println("Original TreeMap: " + originalTreeMap);

        // Displaying the cloned TreeMap object
        System.out.println("Cloned TreeMap: " + clonedTreeMap);

        // Modifying the cloned TreeMap object
        clonedTreeMap.put(4, new Employee(104, "Alice"));

        // Displaying the original TreeMap object after modifying the cloned TreeMap object
        System.out.println("Original TreeMap after modifying the cloned TreeMap: " + originalTreeMap);

        // Displaying the cloned TreeMap object after modifying it
        System.out.println("Cloned TreeMap after modifying it: " + clonedTreeMap);
    }
}

Output:

Original TreeMap: {1=Employee{id=101, name='John'}, 2=Employee{id=102, name='Mary'}, 3=Employee{id=103, name='Bob'}}
Cloned TreeMap: {1=Employee{id=101, name='John'}, 2=Employee{id=102, name='Mary'}, 3=Employee{id=103, name='Bob'}}
Original TreeMap after modifying the cloned TreeMap: {1=Employee{id=101, name='John'}, 2=Employee{id=102, name='Mary'}, 3=Employee{id=103, name='Bob'}}
Cloned TreeMap after modifying it: {1=Employee{id=101, name='John'}, 2=Employee{id=102, name='Mary'}, 3=Employee{id=103, name='Bob'}, 4=Employee{id=104, name='Alice'}}

In the above example, we have created a TreeMap object originalTreeMap with custom objects of the Employee class as values. Then, we have created a shallow copy of the originalTreeMap object using the clone() method and stored it in clonedTreeMap. We have displayed both the original and cloned TreeMap objects. Then, we have modified the clonedTreeMap object by adding a new key-value pair to it. Finally, we have displayed both the original and cloned TreeMap objects again to show that modifying the cloned TreeMap object does not affect the original TreeMap object.