Iterating over HashSet in Java
In our last Java collection tutorial, we have seen How to iterate over ArrayList in Java and in this tutorial we will see How to iterate over HashSet in Java. There are two ways to iterate, loop or traverse over HashSet in Java, first using advanced for-each loop added on Java 5 and second using Iterator which is a more conventional way of iterating over HashSet in Java. Now questions are When should you use for loop and when Iterator is an appropriate option. Well I usually use for loop If I only read from HashSet and doesn't remove any element, while Iterator is preferred approach. You should not remove elements from HashSet while iterating over it in for loop, Use Iterator to do that.
In our last Java collection tutorial, we have seen How to iterate over ArrayList in Java and in this tutorial we will see How to iterate over HashSet in Java. There are two ways to iterate, loop or traverse over HashSet in Java, first using advanced for-each loop added on Java 5 and second using Iterator which is a more conventional way of iterating over HashSet in Java. Now questions are When should you use for loop and when Iterator is an appropriate option. Well I usually use for loop If I only read from HashSet and doesn't remove any element, while Iterator is preferred approach. You should not remove elements from HashSet while iterating over it in for loop, Use Iterator to do that.Iterating over HashSet in Java - Example
In this section, we will see the code example of iterating over HashSet in Java. We have created HashSet and added a couple of String on HashSet and when we iterate, we will print those String one by one in the console.
/**
*
* Java program to Iterate, loop or traverse over HashSet in Java
* This technique can be used to traverse over any other Collection as well
* e.g. traversing over ArrayList or traversing over LinkedList in Java
* @author
*/
public class IteratorTest {
public static void main(String args[]) {
//creating HashSet to iterate over
Set<String> streams = new HashSet<String>();
streams.add("Programming");
streams.add("Development");
streams.add("Debugging");
streams.add("Coding");
// Iterating over HashSet in Java using for-each loop
for(String str : streams){
System.out.println(" Looping over HashSet in Java element : " + str);
}
//Iterating over HashSet using Iterator in Java
Iterator<String> itr = streams.iterator();
while(itr.hasNext()){
System.out.println(" Iterating over HashSet in Java current object: " + itr.next());
}
}
}
Output:
Looping over HashSet in Java element : Coding
Looping over HashSet in Java element : Programming
Looping over HashSet in Java element : Debugging
Looping over HashSet in Java element : Development
Iterating over HashSet in Java current object: Coding
Iterating over HashSet in Java current object: Programming
Iterating over HashSet in Java current object: Debugging
Iterating over HashSet in Java current object: Development
*
* Java program to Iterate, loop or traverse over HashSet in Java
* This technique can be used to traverse over any other Collection as well
* e.g. traversing over ArrayList or traversing over LinkedList in Java
* @author
*/
public class IteratorTest {
public static void main(String args[]) {
//creating HashSet to iterate over
Set<String> streams = new HashSet<String>();
streams.add("Programming");
streams.add("Development");
streams.add("Debugging");
streams.add("Coding");
// Iterating over HashSet in Java using for-each loop
for(String str : streams){
System.out.println(" Looping over HashSet in Java element : " + str);
}
//Iterating over HashSet using Iterator in Java
Iterator<String> itr = streams.iterator();
while(itr.hasNext()){
System.out.println(" Iterating over HashSet in Java current object: " + itr.next());
}
}
}
Output:
Looping over HashSet in Java element : Coding
Looping over HashSet in Java element : Programming
Looping over HashSet in Java element : Debugging
Looping over HashSet in Java element : Development
Iterating over HashSet in Java current object: Coding
Iterating over HashSet in Java current object: Programming
Iterating over HashSet in Java current object: Debugging
Iterating over HashSet in Java current object: Development
That's all on How to iterate over HashSet in Java. Use for each loop if you are just reading from collection and not removing any object from HashSet.
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error Iterator itr = streams.iterator();
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