Java by API/java.util/Iterator

implements Iterator < Character >

   <source lang="java">

import java.util.Iterator; import java.util.NoSuchElementException;

class IterableString implements Iterable<Character>,

                            Iterator<Character> { 
 private String str; 
 private int count = 0; 

 IterableString(String s) { 
   str = s; 
 } 

 public boolean hasNext() { 
   if(count < str.length()) return true; 
   return false; 
 } 

 public Character next() { 
   if(count == str.length())  
     throw new NoSuchElementException(); 

   count++; 
   return str.charAt(count-1); 
 } 

 public void remove() { 
   throw new UnsupportedOperationException(); 
 } 

 public Iterator<Character> iterator() { 
   return this; 
 } 

}

public class MainClass {

 public static void main(String args[]) {  
   IterableString x = new IterableString("This is a test."); 

   for(char ch : x) 
     System.out.print(ch); 

   System.out.println(); 
 }  

}

      </source>
   
  
 
  

Iterator: hasNext()

   <source lang="java">

/**

*Output: 

Original contents of al: C A E B D F Modified list backwards: F+ D+ B+ E+ A+ C+

*/

import java.util.ArrayList; import java.util.Iterator; import java.util.ListIterator; public class MainClass {

 public static void main(String args[]) {
   ArrayList<String> al = new ArrayList<String>();
   al.add("C");
   al.add("A");
   al.add("E");
   al.add("B");
   al.add("D");
   al.add("F");
   System.out.print("Original contents of al: ");
   Iterator<String> itr = al.iterator();
   while (itr.hasNext()) {
     String element = itr.next();
     System.out.print(element + " ");
   }
   System.out.println();
   ListIterator<String> litr = al.listIterator();
   while (litr.hasNext()) {
     String element = litr.next();
     litr.set(element + "+");
   }
   // Now, display the list backwards.
   System.out.print("Modified list backwards: ");
   while (litr.hasPrevious()) {
     String element = litr.previous();
     System.out.print(element + " ");
   }
 }

}

      </source>
   
  
 
  

Iterator: next()

   <source lang="java">

/**

*Output: 

Original contents of al: C A E B D F Modified list backwards: F+ D+ B+ E+ A+ C+

*/

import java.util.ArrayList; import java.util.Iterator; import java.util.ListIterator; public class MainClass {

 public static void main(String args[]) {
   ArrayList<String> al = new ArrayList<String>();
   al.add("C");
   al.add("A");
   al.add("E");
   al.add("B");
   al.add("D");
   al.add("F");
   System.out.print("Original contents of al: ");
   Iterator<String> itr = al.iterator();
   while (itr.hasNext()) {
     String element = itr.next();
     System.out.print(element + " ");
   }
   System.out.println();
   ListIterator<String> litr = al.listIterator();
   while (litr.hasNext()) {
     String element = litr.next();
     litr.set(element + "+");
   }
   // Now, display the list backwards.
   System.out.print("Modified list backwards: ");
   while (litr.hasPrevious()) {
     String element = litr.previous();
     System.out.print(element + " ");
   }
 }

}

      </source>