In this tutorial we will learn how to initialize set in java using various methods . We can create Set in java using constructor , add() method , collections.addAll() method , Anonymous Subclass etc.
1. Java Initialize Set – Using Constructor
We can initialize set in java using constructor . Firstly we initialize array of String then convert array to List and then provide this to TreeSet constructor that accepts another collection . Let’s see java program for java set initialization using constructor .
import java.util.Arrays;
import java.util.Set;
import java.util.TreeSet;
public class JavaInitializeSet {
public static void main(String[] args) {
//initialize array of String
String [] arr = {"php","html","android"};
Set<String> set = new TreeSet<>(Arrays.asList(arr));
//print HashSet element
System.out.println("Set Elements : "+ set);
}
}
Output:
Set Elements : [android, html, php]
2. Java Initialize Set Using add() Method
In this example, We will initialize Set in java using add() method . We create Set by empty constructor and then add elements in this using add() method .
import java.util.Set;
import java.util.TreeSet;
public class JavaInitializeSet1 {
public static void main(String[] args) {
Set<String> set = new TreeSet<String>();
//add element in it
set.add("php");
set.add("html");
set.add("android");
//print the element of Set
System.out.println("Set Elements : "+ set);
}
}
Set Elements : [android, html, php]
3. Initialize Set In Java using Collections.addAll()
We create empty set first . We will create TreeSet and add some elements in it . Now we will provides TreeSet to Collections.addAll() method and it will do set initialization in java with the element of collection (TreeSet).
import java.util.Collections;
import java.util.Set;
import java.util.TreeSet;
public class JavaInitializeSet2 {
public static void main(String[] args) {
Set<String> set = new TreeSet<String>();
TreeSet<String> treeSet = new TreeSet<>();
//add element in treeSet
treeSet.add("php");
treeSet.add("html");
treeSet.add("android");
System.out.println("TreeSet Elements : "+ treeSet);
Collections.addAll(set = treeSet);
System.out.println("Set Elements : "+ set);
}
}
Output:
TreeSet Elements : [android, html, php]
Set Elements : [android, html, php]
4. Java Set Initialization Using Collections.singleton()
import java.util.Collections;
import java.util.Set;
public class JavaInitializeSet3 {
public static void main(String[] args) {
Set<String> set = Collections.singleton("JavaVogue");
System.out.println("Singleton Set : "+ set);
}
}
Singleton Set : [JavaVogue]
5. Initialize Set Java Using Anonymous Subclass
import java.util.Set;
import java.util.TreeSet;
public class JavaInitializeSet4 {
public static void main(String[] args) {
Set<String> set = new TreeSet<String>() {{
add("php");
add("html");
add("android");
}};
System.out.println("Set Elements : "+ set);
}
}
Set Elements : [android, html, php]