This applet shows a number of methods that use arrays. The source code for the methods is also given below.
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There are many kinds of sort programs. These are
examples showing some common ways of writing two simple
sorts: selection sort, and bubble sort.
NOTE: You should rarely, if ever, write your own sort.
Good sorts are available in the Java
library in the java.util.Arrays.sort(...)
and
java.util.Collections.sort(...)
methods.
Here are some questions that you should be able to answer about the sort algorithms.
This method computes the median (middle) value of an array. The array must be sorted before calling this method. It returns the middle element, or the average of the two middle elements if there are an even number of elements. Actually, the entire array doesn't need to be sorted, only up to and including the middle element(s).
//================================================== median // Precondition: Array must be sorted public static double median(double[] m) { int middle = m.length/2; // subscript of middle element if (m.length%2 == 1) { // Odd number of elements -- return the middle one. return m[middle]; } else { // Even number -- return average of middle two // Must cast the numbers to double before dividing. return (m[middle-1] + m[middle]) / 2.0; } }//end method median
Question: Does it matter if the array is sorted in ascending or descending order?
//=============================================== fillRandom public static void fillRandom(int[] a, int min, int max) { int range = max-min; for (int i=0; i < a.length; i++) { a[i] = min + (int)(Math.random()*range); } }//endmethod fillRandom