if Statements and Control Flow

Overview: 3.2.0

• if statements (conditionals) change the flow of control through the program
  • code is only run when something is true
    • Otherwise the block is skipped
• conditionals use the keyword if followed by a boolean expression
  • if (myvar==0)
  • followed by statement or block of statements
    • block statements enclosed by curly brackets

boolean myvariable = true;

if (myvariable) {
  System.out.println("This will only execute if myvariable has a value of true");
}

Relational Operators in if Statements: 3.2.1

• if statements can use relational operators for a boolean condition
  • ==, !=, <, >, <=, >=

int myInteger = 3;
int myOtherInt = 77;

if (myInteger == 3) {
  System.out.println("my integer is 3");
}
if (myOtherInt > 50) {
  System.out.println("My other int is greater than 50");
}

Common Errors: 3.2.2

• Always use curly brackets to enclose a block after the if statement
  • Java doesn’t care about indentation
• Don’t use a semicolon after an if statement
  • Use curly brackets
• Always use ==, not =

Summary: 3.2.4

• if statements test a boolean expression
  • Runs the following statement/block if it is true
• relational operators are used in boolean expressions to compare values and expressions
• if statements affect the flow of control by changing what code executes based on the value of a boolean