TreeSet equals() method in Java with Example

The equals() method of java.util.TreeSet class is used to compare the specified object with this set for equality. Returns true if and only if the specified object is also a set, both sets have the same size, and all corresponding pairs of elements in the two sets are equal. (Two elements e1 and e2 are equal if (e1==null ? e2==null : e1.equals(e2)).) In other words, two sets are defined to be equal if they contain the same elements in the same order.

Syntax:

public boolean equals(Object o)

Parameters: This method takes the object o as a parameter to be compared for equality with this set.

Returns Value: This method returns true if the specified object is equal to this set.

Below are the examples to illustrate the equals() method.

Example 1:

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// Java program to demonstrate equals()
// method of TreeSet
  
import java.util.*;
  
public class GFG {
    public static void main(String[] argv)
    {
  
        // Creating object of TreeSet<String>
        TreeSet<String>
            set1 = new TreeSet<String>();
  
        // Populating set1
        set1.add("A");
        set1.add("B");
        set1.add("C");
        set1.add("D");
        set1.add("E");
  
        // print set1
        System.out.println("First TreeSet: "
                           + set1);
  
        // Creating another object of TreeSet<String>
        TreeSet<String>
            set2 = new TreeSet<String>();
  
        // Populating set2
        set2.add("A");
        set2.add("B");
        set2.add("C");
        set2.add("D");
        set2.add("E");
  
        // print set2
        System.out.println("Second TreeSet: "
                           + set2);
  
        // comparing first TreeSet to another
        // using equals() method
        boolean value
            = set1.equals(set2);
  
        // print the value
        System.out.println("Are both set equal: "
                           + value);
    }
}

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Output:

First TreeSet: [A, B, C, D, E]
Second TreeSet: [A, B, C, D, E]
Are both set equal: true

Example 2:

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// Java program to demonstrate equals()
// method of TreeSet
  
import java.util.*;
  
public class GFG1 {
    public static void main(String[] argv)
    {
  
        // Creating object of TreeSet
        TreeSet<Integer>
            set1 = new TreeSet<Integer>();
  
        // Populating set1
        set1.add(10);
        set1.add(20);
        set1.add(30);
        set1.add(40);
        set1.add(50);
  
        // print set1
        System.out.println("First TreeSet: "
                           + set1);
  
        // Creating another object of TreeSet
        TreeSet<Integer>
            set2 = new TreeSet<Integer>();
  
        // Populating set2
        set2.add(10);
        set2.add(20);
        set2.add(30);
  
        // print set2
        System.out.println("Second TreeSet: "
                           + set2);
  
        // comparing first TreeSet to another
        // using equals() method
        boolean value = set1.equals(set2);
  
        // print the value
        System.out.println("Are both set equal: "
                           + value);
    }
}

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Output:

First TreeSet: [10, 20, 30, 40, 50]
Second TreeSet: [10, 20, 30]
Are both set equal: false


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