7.6. Code Practice with Arrays

Fix the following code so that it prints every other value in the array arr1 starting with the value at index 0.

public class Test { public static void main(String[] args) { int arr1 = {1, 3, 7, 9, 15, 17}; for (int index = 0; index <= arr1.length; index+=2) { System.out.print(index + ", "); } } }

Change line 5 to add the [] on the declaration of arr1 to show that it is an array of integer values. Change line 6 to index < arr1.length so that you don’t go out of bounds (the last valid index is the length minus one). Change line 8 to print arr1[index].

Solution to question above.

public class Test { public static void main(String[] args) { int[] arr1 = {1, 3, 7, 9, 15}; for (int index = 0; index < arr1.length; index+=2) { System.out.print(arr1[index] + ", "); } } }

Fix the following to print the values in the array a1 starting with the value at the last index and then backwards to the value at the first index.

public class Test { public static void main(String[] args) { int[] a1 = {1, 3, 7, 9, 15}; for (int i = a1.length; i > 0; i--) System.out.print(arr[i] + ", "); } }

Rewrite the following code so that it prints all the values in an array arr1 using a for-each loop instead of a for loop.

public class Test { public static void main(String[] args) { int[] arr1 = {1, 3, 7, 9}; for (int index = 0; index < arr1.length; index++) { System.out.print(arr1[index] + ", "); } } }

Finish the following code so that it prints out all of the odd values in the array a1.

public class Test1 { public static void main(String[] args) { int[] a1 = {0, 3, 6, 7, 9, 10}; for (int value : a1) { } } }

Finish the following method getSum to return the sum of all values in the passed array.

public class Test { public static int getSum(int[] arr) { } public static void main(String[] args) { int[] a1 = {1, 2, 5, 3}; System.out.println("It should print 11 " + " and your answer is: " + getSum(a1)); } }

Finish the following method to return the sum of all of the non-negative values in the passed array.

public class Test { public static int getSumNonNeg(int[] arr) { } public static void main(String[] args) { int[] a1 = {1, 2, 5, 3, -1, -20}; System.out.println("The code should print 11 " + "and your answer is: " + getSumNonNeg(a1)); } }

Finish the following code to print the strings at the odd indices in the array.

public class Test1 { public static void main(String[] args) { String[] stArr1 = {"Destini", "Landon", "Anaya", "Gabby", "Evert"}; } }

Finish the method getSumChars below to return the total number of characters in the array of strings strArr.

public class Test { public static int getSumChars(String[] strArr) { } public static void main(String[] args) { String[] strArr = {"hi", "bye", "hola"}; System.out.println(getSumChars(strArr)); } }

Finish the method findMin so that it finds and returns the minimum value in the array.

public class Test { public static int findMin(int[] arr) { } public static void main(String[] args) { int[] arr = {20, -3, 18, 55, 4}; System.out.println(findMin(arr)); } }

Finish the method getAverage to calculate and return the average of all of the values in the array.

public class Test { public static double getAverage(int[] arr) { } public static void main(String[] args) { int[] arr = {20, 3, 18, 55, 4}; System.out.println(getAverage(arr));; } }

7.6.1. More Practice

For practice with simple array manipulation and conditionals, but no loops see http://codingbat.com/java/Array-1. For more practice with loops and arrays go to http://codingbat.com/java/Array-2.

Here are problems without loops

• http://codingbat.com/prob/p167011

• http://codingbat.com/prob/p191991

• http://codingbat.com/prob/p146256

• http://codingbat.com/prob/p199519

• http://codingbat.com/prob/p109537

Here are problems with loops

• http://codingbat.com/prob/p180920

• http://codingbat.com/prob/p104627

• http://codingbat.com/prob/p199612

• http://codingbat.com/prob/p105031

• http://codingbat.com/prob/p100246

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