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Returns true if value of a false, true
                     !      Logical NOT                                                !a             false
                                              otherwise

              3.4 controL FLow
            Remember that a program is nothing more than a list of instructions. Java executes the instructions one after the other,
            in a sequential fashion. However, there are situations when you may find yourself in this situation.
            However, there are situations when you may want to run an instruction only if a condition is met. You might also wish
            to repeat a series of instructions until a condition is met. Java provides selection structures, while for the latter, it
            provides repetition structures.

            3.4.1 Selection Structures

            In real life, you frequently choose your actions based on whether or not a condition is true. If it’s raining outside, let
            say for example, you’ll bring an umbrella; otherwise, you won’t.

                                                         Looking Outside
                                                           the Window






                                                 True          Is it       False
                                                             Raining?



                                          Carry an                           Don’t Carry an
                                          Umbrella                             Umbrella

            Similarly, you might wish to run a section of a program based on the value of an expression. For executing a block of
            code conditionally, Java includes two statements: the if else statement and the switch statement. (A block of code is a
            sequence of statements contained in curly braces.)
            3.4.2 The if-else Statement

            The if statement in Java lets us execute a block of code depending upon whether an expression evaluates to true or
            false. The syntax of the Java if statement is as below:

            if (expression)
            {
            statements

            }
            After the if keyword, the expression in the round brackets is a condition, which is an expression made up of relational
            and logical operators. If the condition evaluates to true, the following block of code is performed; otherwise, it is not.
            The curly braces are optional if the block contains only one statement after the if. Let’s make our Percentage Calculator
            application even better. We will declare the student passed if the percentage obtained by the student is greater than
            or equal to 40%.
            As a result, we write, in our percentage calculator application,

            if (percentage >= 40)
            {



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