Use boolean or boolean in java

 System.out.println(a + "\n" + b + "\n" + c + "\n" + d + "\n" + e); 

1. Петя: “Я не ел. Маша тоже не ела.”
2. Вася: “Маша действительно не ела. Это сделал Петя”
3. Маша: “Вася врет. Это он съел.”

Выясните, кто ел варенье, если известно, что двое из них оба раза сказали правду, а третий один раз соврал, а один раз сказал правду.

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Java Booleans

Very often, in programming, you will need a data type that can only have one of two values, like:

For this, Java has a boolean data type, which can store true or false values.

Boolean Values

A boolean type is declared with the boolean keyword and can only take the values true or false :

Example

boolean isJavaFun = true; boolean isFishTasty = false; System.out.println(isJavaFun); // Outputs true System.out.println(isFishTasty); // Outputs false 

However, it is more common to return boolean values from boolean expressions, for conditional testing (see below).

Boolean Expression

A Boolean expression returns a boolean value: true or false .

This is useful to build logic, and find answers.

For example, you can use a comparison operator, such as the greater than ( > ) operator, to find out if an expression (or a variable) is true or false:

Example

int x = 10; int y = 9; System.out.println(x > y); // returns true, because 10 is higher than 9 

Example

System.out.println(10 > 9); // returns true, because 10 is higher than 9 

In the examples below, we use the equal to ( == ) operator to evaluate an expression:

Example

int x = 10; System.out.println(x == 10); // returns true, because the value of x is equal to 10 

Example

System.out.println(10 == 15); // returns false, because 10 is not equal to 15 

Real Life Example

Let's think of a "real life example" where we need to find out if a person is old enough to vote.

In the example below, we use the >= comparison operator to find out if the age ( 25 ) is greater than OR equal to the voting age limit, which is set to 18 :

Example

int myAge = 25; int votingAge = 18; System.out.println(myAge >= votingAge);

Cool, right? An even better approach (since we are on a roll now), would be to wrap the code above in an if. else statement, so we can perform different actions depending on the result:

Example

Output "Old enough to vote!" if myAge is greater than or equal to 18 . Otherwise output "Not old enough to vote.":

int myAge = 25; int votingAge = 18; if (myAge >= votingAge) < System.out.println("Old enough to vote!"); >else

Booleans are the basis for all Java comparisons and conditions.

You will learn more about conditions ( if. else ) in the next chapter.

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Booleans in Java explained

The datatypes in Java are categorized into two broader categories. One is primitive and the other is the non-primitive data type. Boolean belongs to the primitive data type of Java. Java Boolean variable takes either true or false value, and thus a Boolean variable or expression plays a vital role in decision making for programmers. This article provides an informative guide about Java Boolean and Java expression. The following are the learning outcomes of this guide:

• understanding the working of Boolean variable/expression
• examples that clarify the concept of Boolean in Java

How Boolean works in Java

As discussed earlier, a Boolean variable/expression helps in making a decision between various conditions. The syntax to create a Boolean variable is described below:

• the boolean is the keyword used to declare a Boolean variable in Java
• the variable-name is user-defined a
• lastly, it can store only true/false values, therefore the value may be true/false while declaring a Boolean variable.

The above syntax only considers Boolean variables. Whereas the Boolean expression returns the true or false value after going through the condition.

How to use Boolean variable/expression in Java

This section briefly presents few examples that demonstrate the usage of a Boolean variable and expression.

Example 1: Creating a Boolean variable

Following the syntax in the above section, you can create a Boolean variable. For instance, the following statements create two Boolean variables a and b respectively. Moreover, the value assigned to a is true and false value is stored in b variable.

For better understating, the above statements are used in the following Java code:

public static void main ( String [ ] args ) {

//initializing two boolean variables

System. out . println ( "The value of a : " + a ) ;

System. out . println ( "The value of b is: " + b ) ;

The above code is described as:

The code written above initializes two boolean variables and then prints them. The screenshot of the output is provided below:

Example 2: Getting the Boolean expression for decision

The primary purpose of the Boolean expression is to assist in making the decision. A Boolean expression returns a Boolean value (true/false). The Java code provided below shows several conditions are tested on two integers and returns the Boolean expression true or false (depending on the true/false of condition).

public static void main ( String [ ] args ) {

//initializes two variables

//checking various conditions

System. out . println ( a > b ) ;

System. out . println ( a == b ) ;

The output of the above code is displayed in the following image:

Example 3: Making use of Boolean operators

The Boolean operators help in comparing multiple conditions on Boolean variables. Several logical operators can be applied to Boolean variables and they are referred to as Boolean operators as well. The following code practices few Boolean operators on Boolean variables to get the result on the basis of decisions made by Boolean operators.

public static void main ( String [ ] args ) {

//initializes two boolean variables

boolean a = true , b = false ;

System. out . println ( a | b ) ;

//using NOT(!) and equals(==) operator

System. out . println ( ! ( a == b ) ) ;

The output of the code is provided below:

• initializes two Boolean variables
• applies OR (I) on a and b: The OR operator returns true if one of the a and b values is true.
• applies AND (&) operator on a and b: The AND operator returns false if one a and b is false.
• applies NOT (!) and equal (==) operators: As condition a==b is false, and alongside it NOT(reverses the output) operator is used, so the output will be true.

For further guidance, the following table represents how Boolean OR and AND behave against various Boolean values:

Conclusion

The Boolean variable in Java stores true or false values whereas a Boolean expression returns a true or false value. These terms are used in Java for decision-making and for checking the various conditions. This post provides the demonstration of Boolean variables and expressions in Java. You would have learned the initialization of Boolean variables. Moreover, we have also provided a few examples that show how Boolean variables and expressions can be useful for decision making.

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