Java Tip: How to Sort Arrays in Java using java.util.Arrays class
Here is a small but very useful tip that every Java programmer should be aware of. Have you ever tried sorting arrays in Java? Well, java.util.Arrays class has built in method to make your job easy. You can use following method to sort any array in Java. 
import java.util.Arrays;
...
...
Arrays.sort (int [])
Arrays.sort (String [])
Arrays.sort (float [])
Arrays.sort (double [])
Arrays.sort (long [])
Arrays.sort (Object [])
...

Code language: Java (java)
Let us check an example were we will sort an array of String in ascending as well as descending order. Here is a string array we defined in Java. 
String [] stringArray = {"ab", "aB", "c", "0", "2", "1Ad", "a10"};
  
System.out.println("****** Unsorted String Array *******");
for (String str : stringArray) {
 System.out.println(str);
}

Code language: Java (java)
Output: 
****** unsorted string *******
ab
aB
c
0
2
1Ad
a10
In above code we simple define an array of String and printed its value. Now lets sort this array in ascending order using Arrays.sort() method.

Sort in Ascending Order

//Sort array in ascending order
Arrays.sort(stringArray);

System.out.println("****** Sorted String Array *******");
for (String str : stringArray) {
 System.out.println(str);
}

Code language: Java (java)
Output: 
****** Sorted String Array *******
0
1Ad
2
a10
aB
ab
c
Note that we just sorted an array of String in ascending order using sort method. Wasn’t it easy..

Sort in Descending Order

Now lets try to sort the array in reverse order. For this we will use a different signature of sort method. 
Arrays.sort (Object [], Comparator)

Code language: Java (java)
Following is the code to sort array in reverse order. 
//Sort array in reverse order
Arrays.sort(stringArray, Collections.reverseOrder());

System.out.println("****** Reverse Sorted String Array *******");
for (String str : stringArray) {
 System.out.println(str);
}

Code language: Java (java)
Output: 
****** Reverse Sorted String Array *******
c
ab
aB
a10
2
1Ad
0

Selective Sorting

Using Arrays.sort() method it is possible to sort an array selectively. i.e. if you want a subpart of array to be sorted, that is possible using following method. 
Arrays.sort (Object [], int startIndex, int endIndex)

Code language: Java (java)
In following code we are sorting the array starting from index 3 till the end. 
//Sorting array starting from index 3 till 6
Arrays.sort(stringArray, 3, 6);

System.out.println("****** Selective Sort String Array *******");
for (String str : stringArray) {
 System.out.println(str);
}

Code language: Java (java)
Output: 
****** Selective Sort String Array *******
ab
aB
c
0
1Ad
2
a10
Happy sorting.. :)

View Comments

  • I process quite a few AWR and Statspack reports where SQLNet roundtrips per transaction are extremely high. The solution is to use array passing more efficiently in the calling program. Many times this program is java or javascript. Can you elucidate the method to turn on array passing between Oracle, java and javascript for result sets?

  • I have a question to you

    When I typed "contacts.jsp",

    My eclipse told me that "The markup in the document preceding the root element must be well-formed." in the first line

    Is it wrong or not?
    Due to this problem, I cannot see succesful result.

  • Hello, I have a question to you.

    When I made a "contacts.jsp", It made an error.

    I am using Eclipse Helios, Tomcat 7.0, JDK 1.6,

    Um... What's a problem? In my opinion, JDK couldn't look for this direction about tld....

  • A nice tutorial, but the Arrays.sort() methods uses a tuned quicksort with a time complexity of ) O(n*lgn).. Have a look at other sorting algos Counting Sort,Heap Sort. You shld also tell your users about the stability of the algorithms.

  • Hi All,
    I want a alphanumeric sorting in which small letter comes first and capital letter will come in last.
    Can anyone help me by doing a java code.
    input's like :
    3A
    3A(1)
    3A(2)
    3(A)
    3(A)(1)
    3(A)(2)
    4A
    4A(1)
    4A(2)
    4(A)(1)
    4(A)(2)
    3a
    3(a)(1)
    3(a)(2)
    4a
    4(a)(1)
    4(a)(2)

    out put like:
    3(A)
    3(a)(1)
    3(A)(1)
    3(a)(2)
    3(A)(2)
    3a
    3A
    3A(1)
    3A(2)
    4(a)(1)
    4(A)(1)
    4(a)(2)
    4(A)(2)
    4a
    4A
    4A(1)
    4A(2)

  • in my program
    if am using Arrays.sort()
    getting compile time error .classs expected
    can u plz resolve the problem...

    • U can use sort() method of Arrays Class for sorting the Array Values
      public class SortString {
      public static void main(String[] args) {
      String[] str=new String[5];
      str[0]=”vinod”;
      str[1]=”Anmol”;
      str[2]=”Raju”;
      str[3]=”Dheeraj”;
      str[4]=”Binu”;
      for(int i=0;i<5;i++){
      Arrays.sort(str, 0,5);
      System.out.println(str[i]);
      }
      }
      }
      output is :
      Anmol
      Binu
      Dheeraj
      Raju
      vinod

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Published by
Viral Patel
Tags: arraylists How-To Java
14 years ago

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