Arrays

This chapter introduces arrays, a common multi-dimensional data structure used to store data of the same type. (Note that a class is a "data type" in this sense.) Arrays have some number of dimensions and a number of elements in each dimension. These are established when the array is created. The range of the array's index in each dimension goes from zero to the number of that dimension's elements minus one. A for loop is commonly used to initialize, manipulate, and access the values in an array. Here, we treat one-dimensional arrays, sometimes called vectors.

9. Using an Expression as an Index

Answer:
Yes

Using an Expression as an Index

Using an expression for an array index is a very powerful tool. You often solve a problem by organizing the data into arrays, and then processing that data in a systematic way using variables as indexes. See the below program.

You can, of course, copy this program to your editor, save it and run it. Arrays can get confusing. Playing around with a simple program now will pay off later.


public class ArrayEg2
{
  public static void main ( String[] args )
  {
    double[] val = new double[4];  // an array of double 
                                   // cells initialized to 0.0
    val[0] = 0.12;
    val[1] = 1.43;
    val[2] = 2.98;

    int j = 3;
    System.out.println( "cell 3: " + val[ j   ] );
    System.out.println( "cell 2: " + val[ j-1 ] );

    j = j-2;
    System.out.println( "cell 1: " + val[ j   ] );
   }
}

Question 9:
What does the above program output?
cell 3: 
cell 2: 
cell 1: