Three types of selection statements

Three types of selection statements.

if statement:

Performs an action, if a condition is true; skips it, if false.
Single-selection statement—selects or ignores a single action (or group of actions).

if…else statement:

Performs an action if a condition is true and performs a different action if the condition is false.
Double-selection statement—selects between two different actions (or groups of actions).

switch statement:

Performs one of several actions, based on the value of an expression.
Multiple-selection statement—selects among many different actions (or groups of actions).

if Single-Selection Statement

Pseudocode: If student’s grade is greater than or equal to 60 Print “Passed”	Java Code: if ( studentGrade >= 60 ) System.out.println( "Passed" );
If the condition is false, the Print statement is ignored, and the next pseudocode statement in order is performed.

Indentation

Optional, but recommended
Emphasizes the inherent structure of structured programs

if…else Double-Selection Statement

if…else double-selection statement—specify an action to perform when the condition is true and a different action when the condition is false.

Pseudocode: If student’s grade is greater than or equal to 60 Print “Passed” Else Print “Failed”	Java Code: if ( grade >= 60 ) System.out.println( "Passed" ); else System.out.println( "Failed" );
Note that the body of the else is also indented.

Conditional operator (?:)—shorthand if…else.

Ternary operator (takes three operands)

boolean expression ? the value if the boolean expression is true : the value if the boolean expression evaluates to false

System.out.println(studentGrade >= 60 ? "Passed" : "Failed" );

Nested if else statement:

Need else or not? (click it)

import java.util.Scanner;

public class Tester
{
   public static void main(String [] args)
   {
	int score ;
	char grade;

	Scanner input = new Scanner(System.in);
	System.out.println("Enter your score");
	score = input.nextInt();

        if (score >=90) 
           grade = 'A'; 
        else if (score >=80) 
           grade = 'B'; 
        else if (score >=70) 
           grade = 'C'; 
        else if (score >=60) 
           grade = 'D'; 
        else 
           grade = 'F';

	System.out.println("Your test score is "+ score 
         + ", which is equivalent to the grade " + grade + ".");
   }
}

import java.util.Scanner;

public class Tester
{
   public static void main(String [] args)
   {
	int score ;
	char grade;

	Scanner input = new Scanner(System.in);
	System.out.println("Enter your score");
	score = input.nextInt();

        if (score >=90) 
           grade = 'A'; 
         
        if (score >=80) 
           grade = 'B'; 
         
        if (score >=70) 
           grade = 'C'; 
           
        if (score >=60) 
           grade = 'D'; 
        else    
           grade = 'F';

	System.out.println("Your test score is "+ score 
         + ", which is equivalent to the grade " + grade + ".");
   }
}

A ticket for a movie costs 
(i) $10 for a person who is older than 13; 
(ii) $6 for a senior who is 60 or older 
(iii) $0 for a kid who is 13 or younger.

What is wrong with the following segment?

if(age > 13)
   ticketPrice = 10;
else
   if(age > = 60)
     ticketPrice = 6;

Click here for Nested If-Else.

Click here for dangling else problem

Click here for switch statement