java util Arrays Class - Arrays for manipulating arrays

java.util.Arrays Class

Arrays Class in Java

Java Arrays class contains various methods for manipulating arrays (such as sorting and searching). Java Arrays class contains a static factory that allows arrays to be viewed as lists. You need not to instantiate java.util.Arrays class because all the methods are static methods so that we can call the methods with the class name. The methods in this class all throw a NullPointerException if the specified array reference is null, except where noted.

In this tutorial you can learn about java.util.Arrays class and its examples. And also learn how to use java.util.Arrays class. Following example shows how to use int array with java.util.Arrays class.

How to use int array with java.util.Arrays class Example

/*	How to use int array with java.util.Arrays class Example
	Save with file name ArraysExample.java	*/
import java.util.Arrays;
public class ArraysExample
{
	public static void main(String args[])
	{
		// int ARRAY DECLARATION AND CREATION
		int arr[] = {0,-5,2,5,-1,-4,-3,-2,3,1,4};
		// int ARRAY OUTPUT AS STRING
		System.out.println(Arrays.toString(arr));
		// int ARRAY SORTING
		Arrays.sort(arr);
		// int ARRAY OUTPUT AS STRING AFTER SORTING
		System.out.println("After Sorting");
		System.out.println(Arrays.toString(arr));
		// SEARCHING IN int ARRAY
		int index = Arrays.binarySearch(arr, 3);
		if( index >= 0 )
			System.out.println("3 is Found at Index : " + index);
		else
			System.out.println("3 is NOT Found");
		// FILLING int ARRAY WITH DEFAULT ZERO
		Arrays.fill(arr,0);
		// int ARRAY OUTPUT AFTER FILL
		System.out.println(Arrays.toString(arr));
	}
}

Following example shows how to use double array with java.util.Arrays class.

How to use double array with java.util.Arrays class

/*	How to use double array with java.util.Arrays class
	Save with file name ArraysExample2.java	*/
import java.util.Arrays;
public class ArraysExample2
{
	public static void main(String args[])
	{
		// double ARRAY DECLARATION AND CREATION
		double arr[] = {0.0,-5.0,2.0,5.0,-1.5,-4.0,-3.0,-2.0,3.0,1.5,4.0};
		// double ARRAY OUTPUT AS STRING
		System.out.println(Arrays.toString(arr));
		// double ARRAY SORTING
		Arrays.sort(arr);
		// double ARRAY OUTPUT AS STRING AFTER SORTING
		System.out.println("After Sorting");
		System.out.println(Arrays.toString(arr));
		// SEARCHING IN double ARRAY
		int index = Arrays.binarySearch(arr, 3);
		if( index >= 0 )
			System.out.println("3 is Found at Index : " + index);
		else
			System.out.println("3 is NOT Found");
		// FILLING double ARRAY WITH DEFAULT ZERO
		Arrays.fill(arr,0);
		// double ARRAY OUTPUT AFTER FILL
		System.out.println(Arrays.toString(arr));
	}
}

Note : When filling an object array, the fill() method will copy the same object reference to every cell in the array. After filling the array, if you then change that one reference, the attributes of the object in every cell in the array will be changed.

Following example shows how to use String array with java.util.Arrays class.

How to use String array with java.util.Arrays class

/*	How to use String array with java.util.Arrays class
	Save with file name ArraysExample3.java	*/
import java.util.Arrays;
import java.util.Collections;
public class ArraysExample3
{
	public static void main(String args[])
	{
		// String ARRAY DECLARATION AND CREATION
		String arr[] = {"Java Tutorials","NetBeans Tutorials","Huda Tutorials","C"};
		// String ARRAY OUTPUT AS STRING
		for(int i=0;i<arr.length; i++)
		{
			System.out.println(arr[i]);
		}
		// String ARRAY SORTING
		Arrays.sort(arr);
		// String ARRAY OUTPUT AS STRING AFTER SORTING
		System.out.println("\nAfter Sorting\n");
		for(int i=0;i<arr.length; i++)
		{
			System.out.println(arr[i]);
		}
		// SEARCHING IN String ARRAY
		int index = Arrays.binarySearch(arr, "Huda Tutorials");
		if( index >= 0 )
			System.out.println("\nHuda Tutorials is Found at Index : " + index);
		else
			System.out.println("\nHuda Tutorials is NOT Found");
		// String ARRAY REVERSE ORDER
		Arrays.sort(arr,Collections.reverseOrder());
		// String ARRAY OUTPUT AS STRING AFTER SORTING
		System.out.println("\nAfter Reverse Order\n");
		for(int i=0;i<arr.length; i++)
		{
			System.out.println(arr[i]);
		}
		// FILLING String ARRAY WITH DEFAULT null
		Arrays.fill(arr,null);
		// String ARRAY OUTPUT AFTER FILL
		System.out.println(Arrays.toString(arr));
	}
}