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Methods for Java program to traverse Set collection

　　 Java Examples Comprehensive

In this example, we will learn how to iterate over the elements of a set collection in Java.

To understand this example, you should understand the followingJava programmingTopic:

Example1Use forEach loop to traverse Set

Example

import java.util.Set;
import java.util.HashSet;
class Main {
　　public static void main(String[] args) {
　　　　//Create a set collection
　　　　Set<String> languages = new HashSet<>();
　　　　languages.add("Java");
　　　　languages.add("JavaScript");
　　　　languages.add("Python");
　　　　System.out.println("Set: ");　+　languages);
　　　　//Use forEach loop　
　　　　System.out.println("Iterating over Set using for-foreach loop:")
　　　　for(String language : languages) {
　　　　　　System.out.print(language);
　　　　　　System.out.print(", ");
　　　　}
　　}
}

Output Result

Set: [Java, JavaScript, Python]
Iterating over Set using for-foreach loop:
Java, JavaScript, Python,

In the above example, we created a collection using the HashSet class. Here, we use for-Use a foreach loop to iterate over each element in the collection.

Example2: Use iterator() to traverse the Set

Example

import java.util.Set;
import java.util.HashSet;
import java.util.Iterator;
class Main {
　　public static void main(String[] args) {
　　　　//Create a set collection
　　　　Set<Integer> numbers = new HashSet<>();
　　　　numbers.add(1);
　　　　numbers.add(3);
　　　　numbers.add(2);
　　　　System.out.println("Set: ");　+　numbers);
　　　　//Create an Iterator instance
　　　　Iterator<Integer> iterate = numbers.iterator();
　　　　System.out.println("Traverse Set:");
　　　　while(iterate.hasNext()) {
　　　　　　System.out.print(iterate.next(),　+　", ");
　　　　}
　　}
}

Output Result

Set:　[1,　2,　3]
Traverse Set:
1,　2,　3,

In the above example, we used the HashSet class to create a collection. We used the iterator() method to iterate over the collection. Here,

hasNext() - Returns true if there is a next element in the collection
next() - Return the next element of the collection

Example3: Use the forEach() method to traverse the Set

Example

import java.util.Set;
import java.util.HashSet;
class Main {
　　public static void main(String[] args) {
　　　　//　Create a Set collection
　　　　Set<Integer> numbers = new HashSet<>();
　　　　//Add Element to HashSet
　　　　numbers.add(1);
　　　　numbers.add(2);
　　　　numbers.add(3);
　　　　numbers.add(4);
　　　　System.out.println("Set: ");　+　numbers);
　　　　//Iterate Over Each Element in the Collection
　　　　System.out.print("Element of Set: ");
　　　　//　Access Each Element Using forEach() Method
　　　　//　Passing Lambda Expression to forEach()
　　　　numbers.forEach((e　->　{
　　　　　　System.out.print(e　+　"　");
　　　　});
　　}
}

Output Result

Set:　[1,　2,　3,　4]
Element of Set:　1　2　3　4

In the above example, we created a collection named numbers using the HashSet class. Note the code,

numbers.forEach((e　->　{
　　System.out.print(e　+　"　");
});

Here, we use the forEach() method to access each element in the collection. This method takes a lambda expression as a parameter. For more information about lambda expressions, please visitJava Lambda Expressions.

Java Examples Comprehensive

Java Serialization Java Ternary Operator