Java Nested If

3 Key excerpts on "Java Nested If"

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  eBook - ePub

  ANSI C Programming

  Learn ANSI C step by step

  • Yashavant Kanetkar(Author)
  • 2020(Publication Date)
  • BPB Publications

    (Publisher)

  else . To override this default scope, a pair of braces, as shown in the above example, must be used.

  Nested if-elses

  It is perfectly all right if we write an entireif-else construct within either the body of the if statement or the body of an else statement. This is called ‘nesting’ of if s. This is shown in the following program.

  Note that the second if-else construct is nested in the first else statement. If the condition in the first if statement is false, then the condition in the second if statement is checked. If it is false as well, then the final else statement is executed.

  You can see in the program how each time a if-else construct is nested within another if- else construct, it is also indented to add clarity to the program. Inculcate this habit of indentation; otherwise, you would end up writing programs which nobody (you included) can understand easily at a later date. Note that whether we indent or do not indent the program, it doesn’t alter the flow of execution of instructions in the program.

  In the above program, an if-else occurs within the else block of the first if statement. Similarly, in some other program, an if-else may occur in the if block as well. There is no limit on how deeply the if s and the else s can be nested.

  Forms of if

  The if statement can take any of the following forms:

  Use of Logical Operators

  C allows usage of three logical operators, namely, &&, || and !. These are to be read as ‘AND’ ‘OR’ and ‘NOT’ respectively.

  There are several things to note about these logical operators. Most obviously, two of them are composed of double symbols: || and && . Don’t use the single symbol | and & . These single symbols also have a meaning. They are bitwise operators, which we would examine in Chapter 14 .

  The first two operators, && and|| , allow two or more conditions to be combined in an if

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  eBook - PDF

  Java Programming Fundamentals

  Problem Solving Through Object Oriented Analysis and Design

  • Premchand S. Nair(Author)
  • 2008(Publication Date)
  • CRC Press

    (Publisher)

  Consider the syntax of if and if … else structure you have already learned. For the sake of convenience, those structures are reproduced here. if (logicalExpression) ActionStatement if (logicalExpression) ActionStatement else ActionStatement In the above structures, ActionStatement stands for any executable Java statement, including a block statement. In particular, ActionStatement can be another if or if … else statement. Example 4.19 In this example, we graphically illustrate some of the possible nested structures using if and if … else . The structure shown in Figure 4.4 is an if … else structure nested inside an if structure. The two structures shown in Figure 4.5 are obtained by nesting one if structure inside an if … else . The structure shown in Figure 4.6 is created by nesting two if structures inside an if … else structure. 158 ■ Java Programming Fundamentals FIGURE 4.6 Nesting control structure 3 . logicalExp3 true false logicalExpOne logicalExpTwo true false true false FIGURE 4.4 Nesting control structure 1. logicalExpOne true false logicalExpTwo true false FIGURE 4.5 Nesting control structure 2. logicalExpOne logicalExpTwo true false true false true false logicalExpOne logicalExpTwo true false Decision Making ■ 159 The structure shown in Figure 4.7 shows the nesting of two if … else struc-tures inside an if … else structure. Observe that it can make a four-way decision. The four different selections are logicalExpOne is false and logicalExpTwo is false logicalExpOne is false and logicalExpTwo is true logicalExpOne is true and logicalExp3 is false logicalExpOne is true and logicalExp3 is true Example 4.19 shows that a wide variety of structures can be created through nesting of if and if … else structures. Example 4.20 Consider the income tax rules of a certain country. There is no income tax for the first $25,000.00. The next $75,000.00 is taxed at the rate of 15% and the amount above 100,000.00 is taxed at the rate of 25%.

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  eBook - ePub

  Introduction to Programming and Problem-Solving Using Scala

  • Mark C. Lewis, Lisa Lacher(Authors)
  • 2016(Publication Date)
  • Chapman and Hall/CRC

    (Publisher)

  This is something that we could not do last chapter because we did not have a way of performing logic and making decisions. We could not say that we wanted to do something only in a particular situation. This ability to do different things in different situations is called conditional execution, and it is a very important concept in programming. It is also critical for problem solving in general. Conditional execution gives you the ability to express logic and to solve much more complex problems than you could do without it.

  3.2  The if Expression

  Virtually all programming languages have a construct in them called if. For this construct, you have a condition where one thing should happen if the condition is true. If the condition is false, then either nothing or something different will happen. In non-functional languages, the if construct is a statement. It has no value and simply determines what code will be executed. In Scala and other functional languages, the if is an expression which gives back a value. Scala allows you to use it in either style. The syntax of an if is: if ( condition) trueExpression else falseExpression. The else clause is optional.

  Let us start with an example, then we can broaden it to the more general syntax. Take the ticket price example and consider just the person’s age. Say that we want to consider whether a person should pay the $20 children’s rate or the $35 adult rate. For our purposes, a child is anyone under the age of 13. We could make a variable with the correct value with the following declaration using an if expression.

  val cost = if (age<13) 20 else 35

  This assumes that age is an Int variable that has been defined prior to this point. The first part of this line is a basic variable declaration as discussed in chapter 2 . The next part contains an if expression which checks the age and gives back one of two values depending on whether age<13 is true or false.

  When using if as an expression we always need to include an else because there has to be a value that is given to the variable if the condition is false. This same type of behavior can be also accomplished with a var using the if as a statement

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