cs 6

Chapter 6: More Conditionals and Loops

Overview

• Focuses on:

  • The switch statement

  • The conditional operator

  • The do loop

  • The for loop

  • Using conditionals and loops with graphics

  • Graphic transformations

The Switch Statement

• The switch statement allows decision-making based on the evaluation of an expression, matching its result with predefined cases:

  • General syntax:

    switch (expression) {
        case value1: 
            statement-list1
        case value2: 
            statement-list2
        case value3: 
            statement-list3
        // ...
    }

  • It evaluates the expression and transfers control to the statements of the matching case.

  • A default case can be added using the reserved word default, executed if no cases match.

Break Statement

• A break statement is often used within case statements:

  • Causes control to exit the switch structure.

  • If omitted, control continues to the next case (fall-through behavior).

Example Usage of Switch

• Example switch statement handling grade categories:

  switch (category) {
      case 10:
          System.out.println("a perfect score. Well done.");
          break;
      // Additional cases...
      default:
          System.out.println("not passing.");
  }

Valid Data Types for Switch

• Allowed types for a switch expression include:

  • Integers

  • Characters

  • Enumerated types

  • Strings

• Float types are not allowed, and only equality checks are valid (no relational checks).

The Conditional Operator

• Evaluates to one of two expressions based on a boolean condition:

  • Syntax:

    condition ? expression1 : expression2;

• Similar to an if-else, but returns a value based on the condition's truth.

• Example:

  larger = (num1 > num2) ? num1 : num2;

• Can simplify printing based on conditions:

  System.out.println("Your change is " + count + ((count == 1) ? "Dime" : "Dimes"));

Quick Check Example

• The logic:

  if (val <= 10)
      System.out.println("It is not greater than 10.");
  else
      System.out.println("It is greater than 10.");

• Can be simplified using the conditional operator:

  System.out.println("It is" + ((val <= 10) ? " not" : "") + " greater than 10.");

The do Statement

• Syntax:

  do {
      statement-list;
  } while (condition);

• Executes the statement-list once before evaluating the condition, continuing while it's true.

Example of do Loop

• Example demonstrating a typical do loop for counting:

  int count = 0;
  do {
      count++;
      System.out.println(count);
  } while (count < 5);

The for Statement

• Syntax:

  for (initialization; condition; increment) 
      statement;

• Initialization occurs once before the loop, executing until the condition fails.

Example of for Loop

• Example for counting from 1 to 5:

  for (int count = 1; count <= 5; count++)
      System.out.println(count);

• Demonstrates control based on calculated conditions, performing increments at the end of each iteration.

Using Loops and Conditionals with Graphics

• Graphics can be enhanced by combining conditionals and loops:

  • Example applications include Bullseye.java and Boxes.java.

Graphic Transformations

• JavaFX transforms provide visual changes to nodes, such as:

  • Translation: Changes position along axes.

  • Scaling: Adjusts size of nodes.

  • Rotation: Modifies orientation around a pivot point.

  • Shearing: Alters angles between axes.

Shape Transformation Examples

• Translation Example:

  Rectangle rec2 = new Rectangle(x, y, width, height);
  rec2.setTranslateX(70);
  rec2.setTranslateY(10);

• Scaling Example:

  imgView2.setScaleX(0.7);
  imgView2.setScaleY(0.7);

• Rotation Example:

  rec.setRotate(40);

• Shear Example:

  imgView.getTransforms().add(new Shear(0.4, 0.2));

• Transformations on Groups: When applied to a group, all child nodes inherit the transformation, impacting collective behavior significantly. --

Conclusion

• Chapter 6 emphasized:

  • The switch statement

  • The conditional operator

  • The do loop

  • The for loop

  • Using conditionals and loops with graphics

  • Graphic transformations

By mastering these concepts, improved program design and visual rendering techniques can be implemented.