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Difference between next() and hasNext() in java collections?
Java provides Iterator and ListIterator classes to retrieve the elements of the collection objects.
The hasNext() method
The hasNext() method of these interfaces returns true if the collection object has the next element else it returns false.
Example
import java.util.ArrayList;
import java.util.Iterator;
public class hasNextExample{
public static void main(String[] args){
ArrayList <String> list = new ArrayList<String>();
//Instantiating an ArrayList object
list.add("JavaFX");
list.add("Java");
Iterator<String> it = list.iterator();
System.out.println(it.hasNext());
it.next();
System.out.println(it.hasNext());
it.next();
System.out.println(it.hasNext());
}
}Output
true true false
The next() method
The next() methods of the Iterator and ListIterator returns the next element of the collection.
Example
import java.util.ArrayList;
import java.util.Iterator;
public class nextExample{
public static void main(String[] args){
ArrayList <String> list = new ArrayList<String>();
//Instantiating an ArrayList object
list.add("JavaFX");
list.add("Java");
list.add("WebGL");
list.add("OpenCV");
list.add("OpenNLP");
list.add("JOGL");
list.add("Hadoop");
list.add("HBase");
list.add("Flume");
list.add("Mahout");
list.add("Impala");
System.out.println("Contents of the array list (first to last): ");
Iterator<String> it = list.iterator();
while(it.hasNext()) {
System.out.println(it.next());
}
}
}Output
Contents of the array list (first to last): JavaFX Java WebGL OpenCV OpenNLP JOGL Hadoop HBase Flume Mahout Impala
Updated on: 15-Oct-2019
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