Introduction to Programming (CPSC 124)
—Hobart & William Smith Colleges, Spring 2015
Thursday Lab #7
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Due by the start of class on Friday, 03/27/2015

In this assignment, you will implement a number of methods that are useful when working with arrays. All of the following functions should be added to a single class, ArrayUtils.

A partial implementation is available here:

You will find this lab much easier if you use DrJava as your development environment. Use the Interactions pane to help with quick tests of the various methods.


  1. Write a function, isIn, which takes as arguments an array, A, of double values and a single double value, x. The function should return true if x occurs anywhere in A and false otherwise.

  2. Write a function, concat, which takes as arguments two arrays of double values, A and B. The function should return the array that results from concatenating B onto the end of A (much like the + operator on String objects).

  3. Write a function, repeat, which takes as arguments an array of double values, A, and an integer n. The function should return an array consisting of n copies of A. For example,

    double[] nums = {1.1, 2.2, 3.3};
    double[] moreNums = repeat(nums,3);

    should assign to moreNums the array [1.1, 2.2, 3.3, 1.1, 2.2, 3.3, 1.1, 2.2, 3.3]

  4. Write a function, remove, which takes as arguments an array A of double values, and a single double, n. The function should return a copy of A, with the first occurrence of n removed (HINT: You can do this with an array traversal, but it's much easier to use calls to slice and indexOf).

  5. Write a function, shuffle, which takes as argument an array A of double values. The function should randomly rearrange the contents of A. One way to do this is to traverse the array, and at each index, pick a random location somewhere else in the array, and swap the two elements.

    int j = (int) (Math.random() * A.length);
    double tmp = A[j];
    A[j] = A[i];
    A[i] = tmp;

    There is no return value.

Turn In

The source code for your program,, in a subfolder of your turn-in directory called "lab7". Please also provide a paper copy of your work.

Standards (READ ME)

Formatting Requirements

See the Style Guide, available from the General Notes section of our course web site. Beginning with this assignment, all elements of beautiful, clear code style described there will be expected.


John H. E. Lasseter