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Section 9.13 Chapter Summary

Subsection 9.13.1 Technical Terms

array initializer array length
binary search data structure
element element type
insertion sort multidimensional array
one-dimensional array polymorphic sort method
selection sort sequential search
sorting subscript
two-dimensional array

Subsection 9.13.2 Important Points

  • An array is a named collection of contiguous storage locations, each of which stores a data item of the same data type. Each element of an array is referred to by a subscript β€”that is, by its position in the array. If the array contains N elements, then its length is N and its indexes are 0, 1, N-1.

  • Array elements are referred to using the following subscript notation arrayname[subscript], where arrayname is any valid identifier, and subscript is an integer value in the range 0 to arrayname.length - 1. The array's length instance variable can be used as a bound for loops that process the array.

  • An array declaration provides the name and type of the array. An array instantiation uses the keyword new and causes the compiler to allocate memory for the array's elements:

    int arr[]; // Declare a one-dimensional array variable
    arr = new int[15];// Allocate 15 int locations for it

  • Multidimensional arrays have arrays as their components:

    int twoDarr[][]; // Declare a two-dimensional array variable
    twoDarr = new int[10][15]; // Allocate 150 int locations

  • An array's values must be initialized by assigning values to each array location. An initializer expression may be included as part of the array declaration.

  • Insertion sort and selection sort are examples of array sorting algorithms. Both algorithms require several passes over the array.

  • When an array is passed as a argument to a method, a reference to the array is passed rather than the entire array itself.

  • Swapping two elements of an array, or any two locations in memory, requires the use of a temporary variable.

  • Sequential search and binary search are examples of array searching algorithms. Binary search requires that the array be sorted.

  • For multidimensional arrays, each dimension of the array has its own length variable.

  • Inheritance and polymorphism are useful design features for developing a hierarchy of computer games.

Solutions 9.13.3 Solutions to Self-Study Exercises

9.2 One-Dimensional Arrays
9.2.3 Array Allocation

Self-Study Exercises How many bytes int array? How many bytes double array? How many bytes char array? How many bytes String array? How many bytes Student array?

9.2.5 Assigning and Using Array Values

Self-Study Exercises Assign to the first element.

9.3 Simple Array Examples

Self-Study Exercise

9.4 Example: Counting Letter Frequencies
9.4.2 A Class to Count Letter Frequencies

Self-Study Exercises

9.5 Array Algorithms: Sorting
9.5.1 Insertion Sort

Self Study Exercise

9.5.2 Selection Sort

Self-Study Exercises

9.5.3 Algorithm: Swapping Memory Elements

Self-Study Exercises Swapping values in variables.

9.5.4 Passing a Value and Passing a Reference

Self-Study Exercise

9.6 Array Algorithms: Searching
9.6.2 Binary Search

Self-Study Exercise

9.7 Two-Dimensional Arrays
9.7.1 Example: Rainfall Array

Self-Study Exercises

9.7.3 Passing Part of an Array to a Method

Self-Study Exercises

9.9 OBJECT-ORIENTED DESIGN: Polymorphic Sorting (Optional)
9.9.3 The java.util.Arrays.sort() Method

Self-Study Exercises
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