UNIT 3.3

What if you want to pick between two possibilities? If you are trying to decide between a couple of things to do, you might flip a coin and do one thing if it lands as heads and another if it is tails. In programming, you can use the if keyword followed by a statement or block of statements and then the else keyword also followed by a statement or block of statements.

// A block if/else statementif (boolean expression) { statement1; statement2; } else{ do other statement; and another one; }

// A single if/else statement if (boolean expression) Do statement; else Do other statement;

The else will only execute if the condition is false.

If/else statements can also be used with relational operators and numbers like below. If your code has an if/else statement, you need to test it with 2 test-cases to make sure that both parts of the code work.

If statements can be nested inside other if statements. Sometimes with nested ifs we find a dangling else that could potentially belong to either if statement. The rule is that the else clause will always be a part of the closest unmatched if statement in the same block of code, regardless of indentation.

// Nested if with dangling elseif (boolean expression) if (boolean expression) Do statement; else // belongs to closest if Do other statement;

• If statements can be followed by an associated else part to form a 2-way branch:

**if** (boolean expression) { Do statement; } **else**{ Do other statement; }

A two way selection (if/else) is written when there are two sets of statements: one to be executed when the Boolean condition is true, and another set for when the Boolean condition is false.

The body of the “if” statement is executed when the Boolean condition is true, and the body of the “else” is executed when the Boolean condition is false.

Use 2 test-cases to find errors or validate results to try both branches of an if/else statement.

The else statement attaches to the closest unmatched if statement in the same block of statements.