Control Structures A control structure is simply a pattern for controlling the flow of a program module. The three fundamental control structures of a structured programming language are sequence, selection, and iteration. Sequence control structure is what you have been doing up until now. The second two is what we are going to take a look at next.

Selection/Iteration Structure Selection and Iteration allow the flow of the program to be altered, depending on one or more conditions. Selection is implemented by using a if, if/else, and switch statements. Iteration is implemented by using the while, do/while, and for statements.

The IF statement The if statement works much the same as a if/then statement in Visual Basic. It uses relational operators to test if something is true or false. If it is true, the program will execute the statement(s) within the if statement. If it is false, the program will bypass the statements and continue with the statements following the if statement.

Syntax of the If Statement if (test expression) { statement1; statement2; statement; } //this is an example of a compound statement

if/else Statement The if/else statement works in the same manner as the if/then/else in Visual Basic. It is considered a double-alternative statement. If the expression evaluates as true, then the statements inside the if are executed. If the expression evaluates as false, then the statements inside the else are executed.

Syntax for if/else if (test expression) { statement1; statement2; statement; } else { statement1; statement2; statement; } //example of compound statements

Relational Operators Relational operators allow two quantities to be compared. Mathematical SymbolJavaMeaning == =Equal to  ! =Not equal to <<Less than  < =Less than or equal >>Greater than  > =Greater than or equal

Logical Operators Java

Logical Operators

Example Switch Program import TerminalIO.KeyboardReader; public class ExampleSwitch { public static void main(String [] args) { KeyboardReader reader = new KeyboardReader(); int number; number = reader.readInt("Please enter a number: "); switch (number) { case 1: System.out.println("Your number is 1"); case 2: case 3: case 4: case 5: System.out.println("Your number is between 2 and 5"); break; case 6: case 7: case 8: case 9: case 10:System.out.println("Your number is between 6 and 10"); break; default:System.out.println("Your number is not between 1 and 10"); }

Switch Statement The switch statement works in the same manner as the case select statement in Visual Basic. A selector variable is first evaluated to produce a value. The selector is then compared to a series of cases. If the selector value matches one of the case values, the corresponding case statements are executed.

Syntax for a Switch Statement switch (selector variable) { case case1value :case1statements; break; case case2value :case2statements; break; case casenvalue : case_N_statements; break; default : case exception statements; }

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