Arrays - New features in Java 1.5.0

Enhanced for Loops (see Deitel Ch 7.6)

• The enhanced for statement allows us to iterate through any array or collection without using a counter, the traditional index through the array.
• Format (for arrays):

   for ( parameter : arrayName)
      loop body
  

• Consider a typical loop for adding up the elements of a numerical array:

    int[] values = new int[10];
    // other statements that load array with data...
  
    int total = 0;
    for (int i = 0; i < values.length; i++)
       total = total + values[i];
  
    System.out.println("The total is " + total);
  

• The following code is equivalent, using an enhanced for loop:

    int[] values = new int[10];
    // other statements that load array with data...
  
    int total = 0;
    for (int number : values)
       total = total + number;
  
    System.out.println("The total is " + total);
  

Variable-Length Parameter Lists (see Deitel Ch. 7.11)

• A method can have an unspecified number of arguments, of a specified type
• To do this, follow the type name with an ellipsis (...)
  Format:

    typeName... variableName
  

• The use of the ellipsis can only occur once in a parameter list, and must be at the end

     void doTask(int x, double... values)		// LEGAL
  
     void doThing(double... values, int size)		// ILLEGAL
     void doThing(double... values, int... numbers)	// ILLEGAL
  

• In the doTask method above, a variable amount of double arguments may be passed in. The following are all legal calls:

     double d1, d2, d3, d4;
  
     doTask(5, d1, d2);
     doTask(5, d1, d2, d3);
     doTask(5, d1, d2, d3, d4);
     doTask(5, d1, d2, d3, d4, 3.4, 5.9, 12.4);
  

• Java treats a variable-length list of arguments like an array of items of the same type, so enhanced for-loops can be used on them

     void printStats(double... values)
     {
  	for (double val : values)
  	   System.out.print(val + " ");
     }