Array Practice

These questions are to assess your understanding of arrays.

Question 1

True or False: If you create an array of length 5, you can change your mind later and add a sixth element.

See Answer

False. Once you specify the length of an array, it cannot change! An array created with length 5 will always have exactly 5 elements inside of it.

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Question 2

True or False: The code below will execute without error:

String[] stuff = {"hello", "pickle juice", "nineteen", "balloon"};
stuff[2] = 19;

See Answer

False. Arrays can only hold values of a specific type! The stuff array is declared to be of type String[] so its elements can only be of type String (and 19 is not!).

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Question 3

True or False: The code below will execute without error:

String[] otherStuff = {"19.8", "puzzles", "b3st fr13nD"};

See Answer

True. Even though 19.8 is a double, because we’ve surrounded it in quotes its type is String! So all of the elements of the otherStuff array have the appropriate type.

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Question 4

True or False: The code below will execute without error:

int[] nums = {4, -88, 1095, 7.2, 365};

See Answer

False. Because nums is declared to be of type int[], it can only hold values of type int (and 7.2 is not!).

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Question 5

True or False: The code below will execute without error:

double[] otherNums = {-8.77, 4.96, 100, 98.6};

See Answer

True. Even though 100 can be interpreted as an int and otherNums can only hold double, Java will automatically convert it to a double before storing it into the otherNums array!

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Question 6

True or False: The code below will execute without error:

boolean[] tests = new boolean[3];
tests[0] = true;

See Answer

True. The tests array has length 3, so its valid indices are 0, 1, and 2!

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Question 7

True or False: The code below will execute without error:

String[] words = new String[5];
words[5] = "corgi";

See Answer

False. The words array has length 5, so its valid indices are 0, 1,2, 3, and 4, but not 5!

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Question 8

Write the output that would be produced by the following code:

String[] colors = {"red", "orange", "yellow", "green", "blue", "purple"};
for (int i = 0; i < colors.length; i++) {
    String nextColor = colors[i];
    System.out.print(nextColor.length() + " ");
}

See Answer

The output is

3 6 6 5 4 6 

This is a standard array traversal where we are examining each element of the colors array, and for each element we print out the length of the String (using the String’s length() method).