Sort an array in Java

Question

I m trying to make a program that consists of an array of 10 integers which all has a random value  so far so good   However  now I need to sort them in order from lowest to highest value and then print it onto the screen  how would I go about doing so    Sorry for having so much code for a program that small  I ain t that good with loops  just started working with Java   public static void main String args          int    array   new int 10        array 0      int  Math random   100 1        array 1      int  Math random   100 1        array 2      int  Math random   100 1        array 3      int  Math random   100 1        array 4      int  Math random   100 1        array 5      int  Math random   100 1        array 6      int  Math random   100 1        array 7      int  Math random   100 1        array 8      int  Math random   100 1        array 9      int  Math random   100 1         System out println array 0         array 1         array 2         array 3             array 4         array 5        array 6        array 7             array 8        array 9

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Simply do the following before printing the array - Arrays sort array   Note - you will have to import the arrays class by saying - import java util Arrays

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int   array    2  3  4  5  3  4  2  34  2  56  98  32  54    for  int i   0  i  lt  array length  i          for  int j   0  j  lt  array length  j              if  array i   lt  array j                 int temp   array i               array i    array j               array j    temp

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Add the Line before println and your array gets sorted  Arrays sort  array

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Java 8 provides the option of using streams which can be used to sort int   array as   int   sorted   Arrays stream array  sorted   toArray       option 1 Arrays parallelSort array     option 2   As mentioned in doc for parallelSort       The sorting algorithm is a parallel sort-merge that breaks the array   into sub-arrays that are themselves sorted and then merged  When the   sub-array length reaches a minimum granularity  the sub-array is   sorted using the appropriate Arrays sort method  If the length of the   specified array is less than the minimum granularity  then it is   sorted using the appropriate Arrays sort method  The algorithm   requires a working space no greater than the size of the original   array  The ForkJoin common pool is used to execute any parallel tasks    So if the input array is less than granularity  8192 elements in Java 9 and 4096 in Java 8 I believe   then parallelSort simply calls sequential sort algorithm   Just in case we want to reverse sort the integer array we can make use of comparator as   int   reverseSorted   IntStream of array  boxed                            sorted Comparator reverseOrder    mapToInt i - gt  i  toArray      Since Java has no way to sort primitives with custom comparator  we have to use intermediate boxing or some other third party library which implements such primitive sorting

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Be aware that Arrays sort   method is not thread safe  if your array is a property of a singleton  and used in a multi-threaded enviroment  you should put the sorting code in a synchronized block  or create a copy of the array and order that copy  only the array structure is copied  using the same objects inside   For example   int   array   new int 10         int   arrayCopy   Arrays copyOf array   array  length    Arrays sort arrayCopy       use the arrayCopy

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MOST EFFECTIVE WAY   public static void main String args          int    array   new int 10    creates an array named array to hold 10 int s     for int x  array   for-each loop        x     int  Math random   100 1        Array sort array       for int x  array        System out println x

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I was lazy and added the loops  import java util Arrays    public class Sort       public static void main String args                  int    array   new int 10           for   int i   0   i  lt  array length   i                   array i      int  Math random   100 1                      Arrays sort  array            for   int i   0   i  lt  array length   i                   System out println array i                        Your array has a length of 10  You need one variable  i  which takes the values from 0to 9   for   int i   0    i  lt  array length     i                                                                                              ------  increment   i   i   1                                                    -------------------------- repeat as long i  lt  10         ------------------------------------------ start value of i   Arrays sort  array      Is a library methods that sorts arrays

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See below  it will give you sorted ascending and descending both  import java util Arrays  import java util Collections   public class SortTestArray           Example method for sorting an Integer array    in reverse  amp  normal order      public void sortIntArrayReverseOrder          Integer   arrayToSort   new Integer             new Integer 48           new Integer 5           new Integer 89           new Integer 80           new Integer 81           new Integer 23           new Integer 45           new Integer 16           new Integer 2              System out print  General Order is               for  Integer i   arrayToSort            System out print i intValue                       Arrays sort arrayToSort        System out print   n nAscending Order is             for  Integer i   arrayToSort            System out print i intValue                       Arrays sort arrayToSort  Collections reverseOrder         System out print   n nDescinding Order is           for  Integer i   arrayToSort            System out print i intValue                              param args the command line arguments     public static void main String   args        SortTestArray SortTestArray   new SortTestArray        SortTestArray sortIntArrayReverseOrder         Output will be   General Order is      48 5 89 80 81 23 45 16 2   Ascending Order is    2 5 16 23 45 48 80 81 89   Descinding Order is   89 81 80 48 45 23 16 5 2    Note  You can use Math ranodm instead of adding manual numbers  Let me know if I need to change the code     Good Luck    Cheers

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You can sort a int array with Arrays sort  array

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You may use Arrays sort   function              sort   method is a java util Arrays class method            Declaration   Arrays sort arrName

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just FYI  you can now use Java 8 new API for sorting any type of array using parallelSort  parallelSort uses Fork Join framework introduced in Java 7 to assign the sorting tasks to multiple threads available in the thread pool   the two methods that can be used to sort int array   parallelSort int   a  parallelSort int   a int fromIndex int toIndex

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Take a look at Arrays sort

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We can also use binary search tree for getting sorted array by using in-order traversal method  The code also has implementation of basic binary search tree below   class Util       public static void printInorder Node node                  if  node    null                return                         traverse left child            printInorder node left             System out print node data                      traverse right child            printInorder node right                 public static void sort ArrayList lt Integer gt  al  Node node            if  node    null                return                         sort left child            sort al  node left             al add node data               sort right child            sort al  node right              class Node       Node left      Integer data      Node right       public Node Integer data            this data   data             public void insert Integer element            if element equals data                 return                        if element is less than current then we know we will insert element to left-sub-tree         if element  lt  data                   if this node does not have a sub tree then this is the place we insert the element              if this left    null                    this left   new Node element                   else      if it has left subtree then we should iterate again                  this left insert element                           else               if this right    null                    this right   new Node element                 else                   this right insert element                                    class Tree       Node root       public void insert Integer element            if root    null                root   new Node element             else               root insert element                               public void print             Util printInorder root              public ArrayList lt Integer gt  sort             ArrayList lt Integer gt  al   new ArrayList lt Integer gt             Util sort al  root           return al           public class Test        public static void main String   args             int    array   new int 10            array 0      int  Math random   100 1            array 1      int  Math random   100 1            array 2      int  Math random   100 1            array 3      int  Math random   100 1            array 4      int  Math random   100 1            array 5      int  Math random   100 1            array 6      int  Math random   100 1            array 7      int  Math random   100 1            array 8      int  Math random   100 1            array 9      int  Math random   100 1             Tree tree   new Tree             for  int i   0  i  lt  array length  i                  tree insert array i                       tree print             ArrayList lt Integer gt  al   tree sort                 System out println  sorted array               al forEach item - gt  System out print item

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Arrays sort yourArray    will do the job perfectly

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It may help you understand loops by implementing yourself  See Bubble sort is easy to understand   public void bubbleSort int   array        boolean swapped   true      int j   0      int tmp      while  swapped            swapped   false          j            for  int i   0  i  lt  array length - j  i                  if  array i   gt  array i   1                     tmp   array i                   array i    array i   1                   array i   1    tmp                  swapped   true                                    Of course  you should not use it in production as there are better performing algorithms for large lists such as QuickSort or MergeSort which are implemented by Arrays sort array

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If you want to build the Quick sort algorithm yourself and have more understanding of how it works check the below code     1- Create sort class   class QuickSort       private int input        private int length       public void sort int   numbers            if  numbers    null    numbers length    0                return                    this input   numbers          length   numbers length          quickSort 0  length - 1                       This method implements in-place quicksort algorithm recursively               private void quickSort int low  int high            int i   low          int j   high              pivot is middle index         int pivot   input low    high - low    2               Divide into two arrays         while  i  lt   j                                   As shown in above image  In each iteration  we will identify a                number from left side which is greater then the pivot value  and                a number from right side which is less then the pivot value  Once                search is complete  we can swap both numbers                              while  input i   lt  pivot                    i                              while  input j   gt  pivot                    j--                            if  i  lt   j                    swap i  j                      move index to next position on both sides                 i                    j--                                      calls quickSort   method recursively         if  low  lt  j                quickSort low  j                      if  i  lt  high                quickSort i  high                        private void swap int i  int j            int temp   input i           input i    input j           input j    temp            2- Send your unsorted array to Quicksort class  import java util Arrays    public class QuickSortDemo        public static void main String args                 unsorted integer array         int   unsorted    6  5  3  1  8  7  2  4           System out println  Unsorted array      Arrays toString unsorted            QuickSort algorithm   new QuickSort               sorting integer array using quicksort algorithm         algorithm sort unsorted              printing sorted array         System out println  Sorted array      Arrays toString unsorted              3- Output  Unsorted array   6  5  3  1  8  7  2  4   Sorted array   1  2  3  4  5  6  7  8

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Here is how to use this in your program   public static void main String args          int    array   new int 10        array 0      int  Math random   100 1        array 1      int  Math random   100 1        array 2      int  Math random   100 1        array 3      int  Math random   100 1        array 4      int  Math random   100 1        array 5      int  Math random   100 1        array 6      int  Math random   100 1        array 7      int  Math random   100 1        array 8      int  Math random   100 1        array 9      int  Math random   100 1         Arrays sort array         System out println array 0         array 1         array 2         array 3             array 4         array 5        array 6        array 7             array 8        array 9

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For natural order   Arrays sort array   For reverse Order   Arrays sort array  Collections reverseOrder     --   It is a static method in Collections class which will further call an inner class of itself to return a reverse Comparator

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Loops are also very useful to learn about  esp When using arrays   int   array   new int 10   Random rand   new Random    for  int i   0  i  lt  array length  i        array i    rand nextInt 100    1  Arrays sort array   System out println Arrays toString array       in reverse order for  int i   array length - 1  i  gt   0  i--      System out print array i          System out println

[java] Sort an array in Java

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