p. 140
Annotated Java Code Example:
package shapes;
import java.lang.*;
/*
This class defines a shape with three dimensions
*/
public class Box extends Shape {
int height; // override the Shape height
int depth; // unique to Box
public Box() {
height = 4;
width = 3; // width is inherited from Shape
depth = 2;
}
public int getDepth() {
return depth;
}
public void setDepth(int newDepth) {
depth = newDepth;
}
// super.getWidth is the same as getWidth() here
public int getVolume() {
return height * super.getWidth() * getDepth();
}
}p. 143
Subclassing (extends) example:
package shapes;
public class Shape {
int height;
int width;
public Shape() {
height = 1;
width = 1;
}
public int getHeight() {
return height;
}
public void setHeight(int newHeight) {
height = newHeight;
}
// getWidth() and setWidth() methods go here
}p. 146
Annotated Use of the Box Example Class:
package shapes;
public class TestBox {
public static void main(String[] args) {
// this creates an object called someBox
Box someBox = new Box();
someBox.setDepth(3);
// getHeight() and setHeight() are from Shape
// height shows the height variable from Box
System.out.println (
"The height of Shape is " + someBox.getHeight() +
" and of someBox is " + someBox.height);
// getDepth and getVolume are from Box
System.out.println (
"The depth of someBox is " + someBox.getDepth() +
" and the volume of someBox is " + someBox.getVolume());
}
}p. 149
Conditional Branching:
class ShowQuarter {
public static void main (String args[]) {
int taxMonth = 10;
String taxQuarter;
if (taxMonth == 1 || taxMonth == 2 || taxMonth == 3) {
taxQuarter = "1st Quarter";
} else if (taxMonth == 4 || taxMonth == 5 || taxMonth == 6) {
taxQuarter = "2nd Quarter";
// more conditions would appear here
} else {
taxQuarter = "Not Valid";
}
System.out.println("Your current Tax Quarter is: " + taxQuarter );
}
}Second example for Conditional Branching:
class ShowQuarter2 {
public static void main (String args[]) {
int taxMonth = 10;
String taxQuarter;
// The break statement jumps out of the conditional testing
switch (taxMonth) {
case 1: case 2: case 3:
taxQuarter = "1st Quarter";
break;
case 4: case 5: case 6:
taxQuarter = "2nd Quarter";
break;
// more conditions would appear here
default:
taxQuarter = "Not Valid";
} // end of the switch
System.out.println("Your current Tax Quarter is: " + taxQuarter);
} // end of the main() method
} // end of the classp. 150
Iteration or Looping:
class TestLoops
{
public static void main (String args[]) {
for (int i = 1; i <= 10; i++) {
System.out.println("Loop 1 count is " + i);
}
}
}Exception Handling:
public class TestException {
public static void main(String[] args) {
int numerator = 5, denominator = 0;
int ratio;
try {
ratio = numerator / denominator ;
System.out.println("The ratio is " + ratio);
}
catch (Exception e) {
// This shows an error message on the console
e.printStackTrace();
}
finally {
System.out.println("The end.");
}
}
}p. 151
Variable Scope:
class TestScope {
public static void main (String[] args) {
int currentSalary = 0;
if (currentSalary < 0) {
int currentCommission = 10;
System.out.println("No salary but the commission is " + currentCommission);
}
else {
System.out.println("Salary but no commission.");
}
// This will cause a compilation error.
System.out.println(currentCommission);
}
}Second example for Variable Scope:
class ShowSalary {
static int previousSalary = 0;
int commission = 10;
public static void main (String[] args) {
int currentSalary = 100;
if (currentSalary == 0) {
System.out.println("There is only a commission.");
}
else {
System.out.println("Current salary is " + currentSalary);
}
System.out.println("{Previous salary is " + previousSalary);
// The following would cause a compile error.
// System.out.println(commission);
}
}p. 153
Top of page:
class TestShowSalary
{
public static void main(String[] args)
{
ShowSalary salary1 = new ShowSalary();
ShowSalary salary2 = new ShowSalary();
//
System.out.println("From salary1: " + salary1.previousSalary);
salary2.previousSalary = 300;
System.out.println("After salary2 changed it: " + salary1.previousSalary);
}
}p. 154
Primitive Datatypes:
// decimal equivalent of the letter 'a'
char charDecimal = 97;
// using an actual character inside single quotes
char charChar = 'a';
// octal equivalent of the letter 'a'
char charOctal = '\141';
// Hex value for the letter 'a'
char charHex = 0x0061;
// Unicode (hex) value for the letter 'a'
char charUnicode = '\u0061';p. 155
PetNames class:
class PetNames {
public static main (String args[]) {
String petFriends[ ][ ] = {
{"George", "Snake", "Alligator"},
{"Denise", "Butterfly"},
{"Christine", "Tiger"},
{"Robert", "Parrot", "Dove", "Dog", "Cat"}
};
}
}p. 157
StringBuffer class:
class StringAppend {
public static void main (String args[]) {
StringBuffer stringBuff = new StringBuffer("A string");
stringBuff = stringBuff.append(" is added");
System.out.println(stringBuff.toString());
}
}p. 158
Top of page:
public class TestCast {
public static void main (String args[]) {
byte smallNumber = 10;
int largeNumber;
largeNumber = smallNumber * 5;
System.out.println("largeNumber is " + largeNumber);
// smallNumber = largeNumber;
smallNumber = (byte) largeNumber;
System.out.println("smallNumber is " + smallNumber);
}
}p. 162
Step 4:
package shapes.client;
public class Shape {
int height;
int width;
public Shape() {
height = 1;
width = 1;
}
public int getHeight() {
return height;
}
public void setHeight(int newHeight) {
height = newHeight;
}
public int getWidth() {
return width;
}
public void setWidth(int newWidth) {
width = newWidth;
}
}p. 164
Step 4:
package shapes.client;
public class Box extends Shape {
int height; // override the Shape height
int depth; // unique to Box
public Box() {
height = 4;
width = 3; // the width from Shape
depth = 2;
}
public int getDepth() {
return depth;
}
public void setDepth(int newDepth) {
depth = newDepth;
}
// super.getWidth is the same as getWidth() here
public int getVolume() {
return height * super.getWidth() * getDepth();
}
}p. 165
Step 3:
package shapes.client;
public class TestBox {
public static void main(String[] args) {
// this creates an object called someBox
Box someBox = new Box();
someBox.setDepth(3);
// getHeight() and setHeight() are from Shape
// height shows the height variable from Box
System.out.println (
"The height of Shape is " + someBox.getHeight() +
" and of someBox is " + someBox.height);
// getDepth and getVolume are from Box
System.out.println (
"The depth of someBox is " + someBox.getDepth() +
" and the volume of someBox is " + someBox.getVolume());
}
}p. 166
First sample:
package sample;
public class WrappedClass {
public WrappedClass() {
}
int sumNumbers(int number1, int number2, boolean reallySum) {
int result = 0;
if (reallySum){
result = number1 + number2;
}
return result;
}
}Second sample:
package sample;
public class WrapperClass {
private final WrappedClass contents;
public WrapperClass(WrappedClass newContents) {
contents = newContents;
}
public int sumNumbers(int number1, int number2) {
return contents.sumNumbers(number1, number2, true);
}
}
