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Conditionals and Control Flow

else Statement

The else statement executes a block of code when the condition inside the if statement is false. The else statement is always the last condition.

boolean condition1 = false; if (condition1){ System.out.println("condition1 is true"); } else{ System.out.println("condition1 is not true"); } // Prints: condition1 is not true

else if Statements

else-if statements can be chained together to check multiple conditions. Once a condition is true, a code block will be executed and the conditional statement will be exited.

There can be multiple else-if statements in a single conditional statement.

int testScore = 76; char grade; if (testScore >= 90) { grade = 'A'; } else if (testScore >= 80) { grade = 'B'; } else if (testScore >= 70) { grade = 'C'; } else if (testScore >= 60) { grade = 'D'; } else { grade = 'F'; } System.out.println("Grade: " + grade); // Prints: C

if Statement

An if statement executes a block of code when a specified boolean expression is evaluated as true.

if (true) { System.out.println("This code executes"); } // Prints: This code executes if (false) { System.out.println("This code does not execute"); } // There is no output for the above statement

Nested Conditional Statements

A nested conditional statement is a conditional statement nested inside of another conditional statement. The outer conditional statement is evaluated first; if the condition is true, then the nested conditional statement will be evaluated.

boolean studied = true; boolean wellRested = true; if (wellRested) { System.out.println("Best of luck today!"); if (studied) { System.out.println("You are prepared for your exam!"); } else { System.out.println("Study before your exam!"); } } // Prints: Best of luck today! // Prints: You are prepared for your exam!

AND Operator

The AND logical operator is represented by &&. This operator returns true if the boolean expressions on both sides of the operator are true; otherwise, it returns false.

System.out.println(true && true); // Prints: true System.out.println(true && false); // Prints: false System.out.println(false && true); // Prints: false System.out.println(false && false); // Prints: false

NOT Operator

The NOT logical operator is represented by !. This operator negates the value of a boolean expression.

boolean a = true; System.out.println(!a); // Prints: false System.out.println(!false) // Prints: true

The OR Operator

The logical OR operator is represented by ||. This operator will return true if at least one of the boolean expressions being compared has a true value; otherwise, it will return false.

System.out.println(true || true); // Prints: true System.out.println(true || false); // Prints: true System.out.println(false || true); // Prints: true System.out.println(false || false); // Prints: false

Conditional Operators - Order of Evaluation

If an expression contains multiple conditional operators, the order of evaluation is as follows: Expressions in parentheses -> NOT -> AND -> OR.

boolean foo = true && (!false || true); // true /* (!false || true) is evaluated first because it is contained within parentheses. Then !false is evaluated as true because it uses the NOT operator. Next, (true || true) is evaluation as true. Finally, true && true is evaluated as true meaning foo is true. */