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.