CST 3513

Purpose of If Statements

• Conditional Execution: If statements facilitate the validation or satisfaction of conditions.

• Control Flow: They determine the path of execution based on boolean conditions (true or false).

Structure of If Statements

• Conditional statement syntax:

  • if (condition) { // code to execute if condition is true }

  • else { // code to execute if condition is false }

Using Else If

• The else if ladder expands the control structure to allow for multiple conditional branches:

  • Syntax:

    if (condition1) {
        // code for condition1
    } else if (condition2) {
        // code for condition2
    } else {
        // code if all conditions are false
    }

Logical Operators

• Relational Operators: Used to compare variables and return boolean values.

  • Greater than (>), Less than (<), Equal to (==), Not equal to (!=)

  • Greater than or equal to (>=), Less than or equal to (<=)

• Logical Operators: Used to combine multiple conditions.

  • AND (&&): true if both conditions are true.

  • OR (||): true if at least one condition is true.

  • NOT (!): inverts the truth value.

Example of Logical Operators

• AND vs. OR:

  • Example:

    if (conditionA && conditionB) {
        // code executed if both conditions are true
    }
    if (conditionA || conditionB) {
        // code executed if at least one condition is true
    }

Truth Table for Logical Operators

• Understanding how the logical operations produce results: | Condition A | Condition B | A && B | A || B | |-------------|-------------|--------|--------| | true | true | true | true | | true | false | false | true | | false | true | false | true | | false | false | false | false |

Using If Statements in Java

• Importing Libraries for User Input:

  • import java.util.Scanner;

  • The Scanner class allows capturing user inputs from the keyboard.

  • Example:

    Scanner input = new Scanner(System.in);
    System.out.print("Enter a number: ");
    int userInput = input.nextInt();

Switch Statements

• Switch vs. If-Else:

  • Use switch statements for clean multi-way branching based on distinct cases.

  • Syntax:

    switch (variable) {
        case value1:
            // execute code block
            break;
        case value2:
            // execute code block
            break;
        default:
            // execute if no cases match
    }

  • Each case must have a unique value.

  • The break statement prevents fall-through.

Increment and Decrement Operators

• Increment: ++ (increases value by 1)

• Decrement: -- (decreases value by 1)

• Can be used either as postfix (value++) or prefix (++value) based on the requirement of when the increment/decrement takes place.

Loops in Java

• Types of Loops:

  • While Loop: Executes code as long as a specified condition is true.

    while (condition) {
        // code to execute
    }

  • Do-While Loop: Similar to the while loop, but guarantees at least one execution.

    do {
        // code to execute
    } while (condition);

  • For Loop: Used for iterating over a range of values.

    for (initialization; condition; increment) {
        // code to execute
    }

Comparison of Strings

• Strings are not compared using relational operators due to their reference nature. Instead, the compareTo method is utilized:

  if (string1.compareTo(string2) < 0) {
      // string1 is less than string2
  } else if (string1.compareTo(string2) > 0) {
      // string1 is greater than string2
  } else {
      // strings are equal
  }

• Optional methods for case-insensitive comparisons:

  • equalsIgnoreCase, compareToIgnoreCase.