Java Revision

Distinguish between a class and an object

Distinguish between a class and an object

◦ A class is the blueprint from which individual

objects are created;

◦ And object is an instance of a class.

How would you declare a class called

‘Square’?

How would you declare a class called

‘Square’?

◦ class Square {

◦ }

How would you create an object, called

yellowSquare of a class called Square?

How would you create an object, called

yellowSquare of a class called Square?

◦ Square yellowSquare = new Square();

What is a Java method?

What is a Java method?

◦ A method describes an action that can be carried

out on or by an object

How would you call a method called

‘showSquare’ for an object called

yellowSquare?

How would you call a method called

‘showSquare’ for an object called

yellowSquare?

◦ yellowSquare.showSquare();

From which method does the execution

of a Java application start?

From which method does the execution

of a Java application start?

◦ From method ‘main’

Write down the main method declaration

Write down the main method declaration

◦ public static void main (String[ ] args){

◦ }

List three Java numeric variable types

List three Java numeric variable types

◦ long

◦ short

◦ byte

◦ int

◦ float

◦ double

Put the following Java primitive types in

order, smallest first:

◦ int

◦ long

◦ byte

◦ short

Put the following Java primitive types in

order, smallest first:

◦ byte

◦ short

◦ int

◦ long

How would you declare a Java variable

called length? (Where ‘length’ is the

length of a window in metres)

How would you declare a Java variable

called length? (Where ‘length’ is the

length of a window in metres)

◦ float length;

Declare a final variable called VAT whose

value is 0.18

Declare a final variable called VAT whose

value is 0.18

◦ static final float VAT = 0.18;

Explain the function of this line: System.out.printf ("%1.2f" , this.cost);

Explain the function of this line: System.out.printf ("%1.2f" , this.cost);

◦ It outputs this.cost to two decimal places

Write a line that outputs ‘The total is’ and

the value of instance variable total on the

screen.

Write a line that outputs ‘The total is’ and

the value of instance variable total on the

screen.

◦ System.out.println(“The total is: “ + this.total);

Write a method called outputTriangle

that outputs the values of sides of a

triangle object a, b and c.

Write a method called outputTriangle

that outputs the values of sides of a

triangle object a, b and c.

◦ public void outputTriangle(){

System.out.println (“Side a:” + this.a);

System.out.println (“Side b:” + this.b);

System.out.println (“Side c:” + this.c);

◦ }

Write a method called getVATCost that

calculates and returns the cost (VAT

included) of an object passed to it

(Assume VAT rate is stored in a global

constant variable called VAT)

Write a method called getVATCost that

returns the cost (VAT included) of an

object (chair) passed to it

(Assume VAT rate is stored in a global

constant variable called VAT)

public float getVATCost(){

◦ float VATCost = (this.cost* VAT) + this.cost;

◦ return VATCost;

}

Write a simple Java method called

findArea that finds and outputs the area

of a rectangle object of sides a and b

Write a simple Java method called

findArea that finds and outputs the area

of a rectangle object of sides a and b

◦ public void findArea() {

float area = this.a * this.b;

System.out.println (“Area : “ + this.area + “sq cm”);

◦ }

Implement a case/switch structure in a method (call your method makeMenuChoice) that outputs the following Menu and then writes on the screen the name of the Menu Option chosen.

◦ Main Menu

◦ 1. Enter Student Details

◦ 2. View Classes

◦ 3. View Marks

◦ 4. View Prize Winners

◦ 5. Exit

Implement a case/switch structure in a method (call your method makeMenuChoice) that outputs the following Menu and then writes on the screen the name of the Menu Option chosen. ◦ Main Menu

◦ 1. Enter Student Details

◦ 2. View Classes

◦ 3. View Marks

◦ 4. View Prize Winners

◦ 5. Exit

System.out.println (“Main Menu”);

System.out.println (“1. Enter Student Details”);

System.out.println (“2. View Classes”);

System.out.println (“3. View Marks”);

System.out.println (“4. View Prize Winners”);

System.out.println (“5. Exit”);

byte choice = input.nextByte();

switch (choice) {

case 1: {

System.out.println (“Enter Student Details”);

break;

}

case 2: [ etc ]

}

Name the three types of Java looping

structures

Name the three types of Java looping

structures

◦ for

◦ while

◦ do..while

Answer True or False

◦ A For Loop is a predetermined loop

◦ A do..while loop will loop 0 or more times

◦ A while..do loop will loop one or more times

Answer True or False

◦ A For Loop is a predetermined loop True

◦ A do..while loop will loop 0 or more times False

◦ A while..do loop will loop one or more times

False

Write a method called handleTest that reads 10 marks into an array called markList.

Write a method called findHighest that finds and outputs the highest mark in array markList

Write a method called findLowest that finds and outputs the lowest mark in array markList

Write a method called findAverage that finds and outputs the average mark in array markList

Write a method called handleTest that reads 10 marks into an array called markList.

public void handleTest() {

int[] markList = new int[10]

for (i = 0; i<10; i++){

System.out.println (‘Enter mark’);

this.markList[i] = input.nextInt();

}

}

Write a method called findHighest that finds and outputs the highest mark in array markList

public void findHighest() {

int i;

int highest = 0;

for (i = 0; i <10; i++) {

if (markList[i] > highest){

highest = markList[i];

}

System.out.println (“The Highest Mark is “ + highest);

}

}