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 executesif (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!
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: falseSystem.out.println(!false) // Prints: true
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: trueSystem.out.println(true && false); // Prints: falseSystem.out.println(false && true); // Prints: falseSystem.out.println(false && false); // Prints: false
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: trueSystem.out.println(true || false); // Prints: trueSystem.out.println(false || true); // Prints: trueSystem.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. */
