./curric/basics/Loops/

Loops

• for
  • The for statement provides a compact way to iterate over a range of values

      for (initialization; termination; increment) {
      statement(s) 
      }
    

  • The initialization expression initializes the loop; it’s executed once, as the loop begins.
  • When the termination expression evaluates to false, the loop terminates.
  • The increment expression is invoked after each iteration through the loop; it is perfectly acceptable for this expression to increment or decrement a value.

      for (int i = 0; i < 11; i++) {
      System.out.println(i); // prints every i used in the loop
      }
    

    Output

      0
      1
      2
      3
      4
      5
      6
      7
      8
      9
      10
    

• while
  • The while statement continually executes a block of statements while a particular condition is true.

      while (expression) {
      statement(s)
      }
    

  • Unlike for loops, in while loops you have the initialization, termination, and increment all done separately.

      int i = 0;
      while (i < 11) {
      System.out.println(i); // prints every i used in the loop
      i++;
      }
    

    Output (same as for)

      0
      1
      2
      3
      4
      5
      6
      7
      8
      9
      10
    

• Enhanced for and Iterators
  • Enhanced for loops or more commonly know as for each loops, use the individual values in the collection instead of the index. For example: ```java int[] arr = new int[] {1, 2, 3, 4, 5}; // array creation shorthand

  // using for loop to print every element for (int i = 0; i < arr.length; i++) { System.out.print(arr[i]); } // 12345

  // using for each to print every element for (int i : arr) { System.out.print(i); } // 12345 ``` Both outputs are the same. But they don’t act the same way. In the for loop, we are using an index to get every element. However in the for each loop, the element gets copied into the the variable i. for each loops are used in situations where you don’t need the index of an element, while for loops are when the index of the element plays an important role.