Iterate without an index

Many programmers have a strong preference for using a for-each loop or an Iterator instead of a for-loop.

The traditional for-loop always uses an explicit loop index - an integer that identifies each iteration. The problem is that loop indexes have always been a fruitful source of error. For example, off-by-one errors are very common in programming, and they are often related to these loop indexes. In addition, the (somewhat unnatural) computer science tradition of starting loop indexes from 0 instead of 1 often contributes to these sorts of bugs.

Since they are more error prone, for-loops with indexes should generally be avoided, in favor of the more robust, compact, and elegant for-each loop.

Example


import java.util.*;

/** Different iteration styles. */
public class IterateNoIndex {
   
  /** 
  * Iterating without an index is more compact and less 
  * error prone. 
  */
   public void withoutIndex(){

     //for-each loop is usually preferred
     List<String> trees = Arrays.asList("Maple", "Birch", "Poplar");
     for(String tree: trees){
       log(tree);
     }
     
     //Iterators are not as compact as a for-each loop
     //but sometimes you need them: removing/replacing items,
     //and 'parallel' iterations across two data structures
     Iterator<String> iter = trees.iterator();
     while (iter.hasNext()) {
       log(iter.next());
     }
   }
   
   /** Iterating with an index is more error prone. */
   public void withIndex(){
     //traditional for-loop
     for(int idx=0; idx < 10; ++idx){
       log("Iteration..." + idx);
     }
   }
   
   // PRIVATE
   private void log(String aMessage){
     System.out.println(aMessage);
   }
}
 



See Also :
Two ways of using Iterator
Use for-each liberally
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