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Java boolean Array - How to Initialize a boolean Array in Java

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boolean Array

boolean Array in Java

Java boolean Array

Java boolean array is used to store boolean data type values only . The default value of the boolean elements in a Java boolean array is false . The default value for a Boolean ( object ) is null . The default value for a boolean ( primitive ) is false .

Java boolean keyword is used to declare a variable as a boolean type which represents only one of two possible values i.e. either true or false . By default boolean variables are initialized with false in Java programming language.

A boolean array is declared with the boolean keyword. The elements of a boolean array can only take the values true or false.

The Default value of boolean is false and wrapper class Boolean is null. With the following Java boolean array examples you can learn

Java boolean Array Topics

What does boolean mean in Java ?

boolean is a primitive data type in Java . boolean means true or false i.e. logical true or false .

What is a boolean Data Type in Java ?

boolean is a primitive data type in Java . boolean means true or false i.e. logical true or false . It occupies 1 bit in memory . These values do not correspond to 1 or 0 as in C or C++ . The following example shows how to use boolean data type in Java .

The boolean Primitive Data Type in Java Programming Language

  1. The boolean is a primitive data type in Java.
  2. The boolean data type is used for logical values.
  3. The boolean data type can have two possible values true or false.
  4. The boolean is the type returned by all relational operators.
  5. The boolean is the type required by the conditional expressions used in control statements such as if , for and while so on.
  6. Boolean is wrapper class for boolean primitive data type.
  7. The boolean primitive data type is also used in creating boolean array.

How many ways to use boolean value in Java ?

  • The boolean value is used to check whether condition is true or false .
  • You can use boolean true value in while loop condition for infinite loop .
  • No need to do == to check equality

Following example shows Java boolean Data Type Example . Save the following Java boolean Data Type Example program with file name JavaBooleanDataType.java .

Java boolean Data Type Example

public class JavaBooleanDataType
{
	public static void main(String args[])
	{
		boolean b;
		System.out.println("Java boolean Data Type Example");
		b = true;
		System.out.println("Assigned boolean Value : " + b);
	}
}

What is a boolean array ?

A Boolean array is a sequence of values that can only hold the values of true or false i.e. boolean data type. In other words a Boolean can only be true or false and is unable to hold any other value.

What is a boolean array in Java ?

Java boolean array is used to store boolean data type values only . The default value of the boolean elements in a Java boolean array is false . The default value for a Boolean ( object ) is null . The default value for a boolean ( primitive ) is false .

Related : Java byte Array

Declaring and Initializing boolean Array

How to declare boolean Array in Java ?

Arrays are declared with [] (square brackets) . If you put [] (square brackets) after any variable of any type only that variable is of type array remaining variables in that declaration are not array variables those are normal variables of that type .

If you put [] (square brackets) after any data type all the variables in that declaration are array variables . All the elements in the array are accessed with index . The array element index is starting from 0 to n-1 number i.e. if the array has 5 elements then starting index is 0 and ending index is 4 .

boolean[] booleanArray;
boolean booleanArray[];

How can we initialize a boolean array in Java ?

The Java boolean array can be used to store boolean datatype values only and the default value of the boolean array is false . An array of booleans are initialized to false and arrays of reference types are initialized to null . In some cases, we need to initialize all values of the boolean array with true or false . We can use the Arrays.fill() method in such cases .

The boolean array will be initialized to false when you allocate it . All arrays in Java are initialized to the default value for the type . This means that arrays of ints are initialised to 0, arrays of booleans are initialised to false and arrays of reference types are initialised to null .

boolean[] booleanArray = new boolean[10];
boolean booleanArray[] = new boolean[7];

What is the Initial or Default Value of boolean Array in Java ?

The default value for a Boolean (object) is null.
The default value for a boolean (primitive) is false.

The default value of any Object, such as Boolean, is null.

The default value for a boolean array is false.

What is the default value of boolean array in Java ?

The default value of boolean array in Java is false. Because the Java boolean default value is false. So all the elements in a Java boolean array holds the default value is false.

What is the Length of an Array in Java ?

In Java all the arrays are indexed and declared by int only . That is the size of an array must be specified by an int value and not long or short . All the arrays index beginning from 0 to ends at 2147483646 . You can store elements upto 2147483647 . If you try to store long (big) elements in array, you will get performance problems . If you overcome performance problems you should go to java collections framework or simply use Vector.

Syntax :

  • < data type > < variable >[];
  • < data type >[] < variable >;

Related : Java char Array

Java boolean Array Example

Following example shows Java boolean Array Example . Save the following Java boolean Array Example program with file name JavaBooleanArray.java .

public class JavaBooleanArray
{
	public static void main(String args[])
	{
		boolean array[];
		array = new boolean[4];
		array[0] = true;
		array[1] = false;
		array[2] = false;
		array[3] = false;
		System.out.println("Java boolean Array Example");
		for(int i=0; < array.length;i++)
		{
			System.out.println("boolean array Element at : "+ i + " " + array[i]);
		}
	}
}

Assigning Values to boolean Array

How to assign values to Java boolean array at the time of declaration ?

In this example you can learn how to assign values to Java boolean array at the time of declaration .

Following example shows How to assign values to Java boolean array at the time of declaration . Save the following assign values to Java boolean array at the time of declaration program with file name AssignValuesToBooleanArray.java .

Assign values to Java boolean array at the time of declaration Example

public class AssignValuesToBooleanArray
{
	public static void main(String args[])
	{
		boolean array[] = {false,false,true,true};
		System.out.println("Java boolean Array Example");
		for(int i=0;i < array.length;i++)
		{
			System.out.println("boolean array Element at : "+ i + " " + array[i]);
		}
	}
}

Related : Java short Array

How to declare Java boolean array with other boolean variables ?

In this example you can learn how to declare Java boolean array with other boolean variables .

Following example shows How to declare Java boolean array with other boolean variables . Save the following declare Java boolean array with other boolean variables program with file name DeclareBooleanArrayWithOtherBooleanVariables.java .

Declare Java boolean array with other boolean variables Example

public class DeclareBooleanArrayWithOtherBooleanVariables
{
	public static void main(String args[])
	{
		boolean array1[], a;
		array1 = new boolean[5];
		array1[0] = true;
		array1[1] = false;
		array1[2] = false;
		array1[3] = false;
		a = true;
		System.out.println("Java boolean Array Example");
		System.out.println("a value is : "+a);
		for(int i=0;i < array1.length;i++)
		{
			System.out.println("boolean array1 Element at : "+ i + " " + array1[i]);
		}
	}
}

How to assign Java boolean array to other Java boolean array ?

In this example you can learn how to assign Java boolean array to other Java boolean array .

Following example shows How to assign Java boolean array to other Java boolean array . Save the following assign Java boolean array to other Java boolean array program with file name AssignBooleanArrayToBooleanArray.java .

Assign Java boolean array to other Java boolean array Example

public class AssignBooleanArrayToBooleanArray
{
	public static void main(String args[])
	{
		boolean[] array1, array2;
		array2 = new boolean[5];
		array2[0] = true;
		array2[1] = false;
		array2[2] = false;
		array2[3] = false;
		array1 = array2;
		System.out.println("Java boolean Array Example");
		System.out.println("array2 array values");
		for(int i=0;i < array2.length;i++)
		{
			System.out.println("boolean array2 Element at : "+ i + " " + array2[i]);
		}
		System.out.println("array1 array values");
		for(int i=0;i < array1.length;i++)
		{
			System.out.println("boolean array1 Element at : "+ i + " " + array1[i]);
		}
	}
}

Filling boolean Array with All true or false

How to fill boolean Array with all true in Java ?

With the Arrays.fill method you can fill boolean array with all true . The java.util.Arrays.fill(boolean[] a, boolean val) method assigns the specified boolean value to each element of the specified array of booleans . Below example shows how to use Arrays.fill method .

In the following example you can learn how to assign all the elements of Java boolean array to true or fill the Java boolean array with true or how to set Java boolean Array all true .

Following example shows Assign all the elements of Java boolean array to true Example . Save the following Fill Boolean Array True Example program with file name FillBooleanArrayExampleTrue.java .

Assign all the elements of Java boolean array to true Example

import java.util.Arrays;
public class FillBooleanArrayExampleTrue
{
	public static void main(String args[])
	{
		boolean[] seats = new boolean[10];
		Arrays.fill(seats, true);
		System.out.println("seats array values");
		for(int i=0;i < seats.length;i++)
		{
			System.out.println("boolean array Element at : "+ i + " " + seats[i]);
		}
	}
}

How to initialize all the boolean array elements to Boolean false ?

If you need to initialize all the boolean array elements to Boolean false . Either use boolean[] instead so that all values defaults to false . you can initialize boolean array using the following ways .

boolean[] array = new boolean[size];

Or use java.util.Arrays to fill the entire array with Boolean.FALSE.

Boolean[] array = new Boolean[size];
Arrays.fill(array, Boolean.FALSE);

Related : Java int Array

What is java.util.Arrays.fill(boolean[], boolean) Method ?

The java.util.Arrays.fill(boolean[] boolean_array, boolean boolean_value) method assigns the specified boolean value to each element of the specified array of booleans.

How to fill boolean Array with all false in Java ?

With the Arrays.fill method you can fill boolean array with all false . The java.util.Arrays.fill(boolean[] a, boolean val) method assigns the specified boolean value to each element of the specified array of booleans . Below example shows how to use Arrays.fill method .

In the following example you can learn how to assign all the elements of Java boolean array to false or fill Java boolean array with false . Following example shows Assign all the elements of Java boolean array to false Example . Save the following Fill Boolean Array False Example program with file name FillBooleanArrayExampleFalse.java .

Assign all the elements of Java boolean array to false Example

import java.util.Arrays;
public class FillBooleanArrayExampleFalse
{
	public static void main(String args[])
	{
		boolean[] seats = new boolean[10];
		Arrays.fill(seats, false);
		System.out.println("seats array values");
		for(int i=0;i < seats.length;i++)
		{
			System.out.println("boolean array Element at : "+ i + " " + seats[i]);
		}
	}
}

Related : Java float Array

Converting boolean array

How to Convert boolean Array to int array in Java ?

In the following example you can learn how to convert Java boolean array into Java int array .

Following example shows How to Convert Java boolean array into Java int array Example . Save the following Convert Java boolean array into Java int array Example program with file name ConvertBooleanArrayToIntArray.java .

How to Convert Java boolean array into Java int array Example

public class ConvertBooleanArrayToIntArray
{
	public static void main(String args[])
	{
		boolean boolean_array[] = {true, false, true, true};
		int boolean_to_int[] = new int[boolean_array.length];
		for(int i=0;i < boolean_array.length;i++)
		{
				if(boolean_array[i])
				{
					boolean_to_int[i] = 1;
				}
				else
				{
					boolean_to_int[i] = 0;
				}
		}
		System.out.println("converted boolean to int array values");
		for(int i=0;i < boolean_to_int.length;i++)
		{
			System.out.println("int array Element at : "+ i + " " + boolean_to_int[i]);
		}
	}
}

Related : Java long Array

How to Convert boolean Array to String in Java ?

The java.util.Arrays.toString(boolean[]) method returns a string representation of the contents of the specified boolean array . The string representation consists of a list of the array's elements, enclosed in square brackets ("[]") . Adjacent elements are separated by the characters ", " (a comma followed by a space) .

The following example shows the usage of java.util.Arrays.toString() method .

Following example shows How to Convert Java boolean array to String Example . Save the following Convert Java boolean array to String Example program with file name ConvertBooleanArrayToString.java .

How to Convert Java boolean array to String Example

public class ConvertBooleanArrayToString
{
	public static void main(String args[])
	{
		boolean boolean_array[] = {true, false, true, true};
		System.out.println("converted boolean array to String");
		System.out.println(Arrays.toString(boolean_array);
	}
}

Set boolean array to false or true

How do you set a boolean array to false?

You can set a Java boolean array to false by following ways.

  1. By creating the array will set all the elements of boolean array initialized by default to false. In Java boolean array elements automatically are assigned the value false because false is the default value of primitive boolean data type .
  2. By Manually set each element value to false.
  3. By Arrays.fill() Method. This is the easiest way to fill boolean array to false. Note : Arrays.fill() method replace all the elements of the original boolean array to false. This is very useful when reset boolean array after use.

How do you set a boolean array to false Example

Following example shows How do you set a boolean array to false . Save the following set a boolean array to false example program with file name BooleanArraySetToFalse.java .

import java.util.Arrays;
public class BooleanArraySetToFalse
{
	public static void main(String args[])
	{
		// BY CREATING THE BOOLEAN ARRAY
		boolean boolean_array[] = new boolean[4];
		System.out.println(Arrays.toString(boolean_array));
		boolean_array[2] = true;
		// BOOLEAN ARRAY OUTPUT AFTER SET 3RD ELEMENT TO TRUE
		System.out.println(Arrays.toString(boolean_array));
		for (int i = 0; i < boolean_array.length; i++)
		{
			boolean_array[i] = false;
		}
		// BOOLEAN ARRAY OUTPUT AFTER SET ALL ELEMENTS TO FALSE
		System.out.println(Arrays.toString(boolean_array));
		// THE EASIEST WAY TO FILL BOOLEAN ARRAY TO FALSE.
		Arrays.fill(boolean_array, false);
		System.out.println(Arrays.toString(boolean_array));
	}
}

How Set all values of ArrayList<Boolean> to false on instantiation ?

An ease way to create an ArrayList<Boolean> using Java and have them initially all set to false without looping through and assigning each to false.

List<Boolean> list=new ArrayList<Boolean>(Arrays.asList(new Boolean[10]));

Collections.fill(list, Boolean.False);

Related : Java double Array

How Set all values of ArrayList<Boolean> to false on instantiation ?

Following example shows How Set all values of ArrayList<Boolean> to false on instantiation . Save the following Set all values of ArrayList<Boolean> to false on instantiation example program with file name SetAllFalse.java . Please note in the SetAllFalse.java program the import statement import java.util.* is used in detail, the import statements import java.util.List, import java.util.ArrayList, import java.util.Arrays, import java.util.Collections used.

import java.util.*;
public class SetAllFalse
{
	public static void main(String args[])
	{
		List<Boolean> list = new ArrayList<Boolean>(Arrays.asList(new Boolean[10]));
		Collections.fill(list, false);
		System.out.println(list);
	}
}