Question

JAVA INTERFACE

1.Suppose you want to design a class that is given numbers one at a time. The class computes the smallest, second smallest, and average of the numbers that have been seen so far. Create an interface for the class. Create a class that implements the interface.

2. Create an interface Measurable with methods getarea( )and getperimeter(). Implement it in two classes Circle, and Square . Both the classes should have Constructor for initializing the dimensions, and define the interface methods.

Create a class client which creates an object of Circle and Square and call their methods.

Answer 1

Please find the answer

create a package and create all class and Interface with the same name as given below inside the package and copy code as given .

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Answer 1- all Classes and Interface

Interface -->

ComputeNumber.java

public interface ComputeNumber {

void smallest(int[] arr);

void secondSmallest(int[] arr);

void average(int[] arr);

}

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implementation class

ComputeNumberImpl.java

public class ComputeNumberImpl implements ComputeNumber {

/**

* this smallest(int[] arr) method is the implementation of ComputerNumber Interface

* here we calculate the smallest of give number of array

* in this method we pass the array as argument

*/

@Override

public void smallest(int[] arr) {

// first suppose the array at zero position store in a variable

// and compare the value loop through the each element of array

// if the smallest number is found at arr[i] position then it store in smallestNumber variable and print it

int smallestNumber = arr[0];

for (int i = 0; i < arr.length; i++) {

if (arr[i] < smallestNumber) {

smallestNumber = arr[i];

}

}

System.out.println("Smallest Number is = " + smallestNumber);

}

/**

* this second smallest(int[] arr) method is the implementation of ComputerNumber Interface

* here we calculate the second smallest number of the given array

* in this method we pass the array as argument

*/

@Override

public void secondSmallest(int[] arr) {

// here take a vaibale temp and it is to swap a element

// here two loop i and j

// first loop for array element at zero position and compare these value to next value from it

// if the element arr[i] found the first smallest and arr[j] found second smallest swap it and

int temp;

for (int i = 0; i < arr.length; i++) {

for (int j = i + 1; j < arr.length; j++) {

if (arr[i] > arr[j]) {

temp = arr[i];

arr[i] = arr[j];

arr[j] = temp;

}

}

}

// second smallest value is store at arr[1] means second position of array and print it

System.out.println("Second Smallest Number = " + arr[1]);

}

/**

* this average(int[] arr) method is the implementation of ComputerNumber Interface

* here we calculate the average number of the given array

* in this method we pass the array as argument

*/

@Override

public void average(int[] arr) {

double average,sum=0;

//calculate size of array

int size =arr.length;

for (int i = 0; i < arr.length; i++) {

sum=sum+arr[i];

}

// average is sum/size

average=sum/size;

// print the average value

System.out.println("Smallest Number is = " + average);

}

}

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Main class to compute the smallest , second smallest and average of number

ComputeNumberMain.java

public class ComputeNumberMain {

public static void main(String[] args) {

//take a array of number and pass this array into a method

int arr[] = { 23, 6, 43, 8, 9, 10 };

// create the object of ComputeNumberImpl

ComputeNumberImpl obj = new ComputeNumberImpl();

// object call the smallest method to print the smallest number;

obj.smallest(arr);

// object call the secondSmallest method to print the second smallest number;

obj.secondSmallest(arr);

// object call the average method to print the average number;

obj.average(arr);

}

}

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Output

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Answer 2- Classes and Interface

Interface

Measurable.java

public interface Measurable {

void getarea();

void getperimeter();

}

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Circle class and this circle class implements Mesurable Interface

Circle.java

public class Circle implements Measurable {

double radius;

// constructor create to pass the radius of each method

Circle(int radius)

{

this.radius=radius;

}

// method to print the area of circle

@Override

public void getarea() {

  

double area;

// area = PI*radius*radius here PI=3.14 but we use Math.PI of java

area=radius*radius*Math.PI;

// here we use printf to format value at two decimal place here .2f is use for this purpose

System.out.printf("Area of Circle = %.2f \n" , area);

}

// method to print the perimeter of circle

@Override

public void getperimeter() {

double perimeter;

// perimeter = 2*radius*PI here PI=3.14 but we use Math.PI of java

perimeter=2*radius*Math.PI;

// here we use printf to format value at two decimal place here .2f is use for this purpose

System.out.printf("Perimeter of Circle = %.2f",perimeter);

System.out.println("");

}  

}

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Square class and this Square class implements Mesurable Interface

Square.java

public class Square implements Measurable {

//variable declare

double side;

//constructor

Square(double side) {

this.side = side;

}

@Override

public void getarea() {

// area of square side*side

double area;

area = side * side;

// here we use printf to format value at two decimal place here .2f is use for

// this purpose

System.out.printf("Area of Square = %.2f \n", area);

}

@Override

public void getperimeter() {

// perimeter of square is 4*side

double perimeter;

perimeter = 4*side;

// here we use printf to format value at two decimal place here .2f is use for

// this purpose

System.out.printf("Perimeter of Square = %.2f \n", perimeter);

}

}

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Main class i.e Client

// client class

public class Client {

public static void main(String[] args) {

//value pass for radius of circle

// here object is create for Circle class

Circle circle=new Circle(4);

circle.getarea();

circle.getperimeter();

//for space

System.out.println(" ");

// here object is create for Square class

//and pass the value to constructor of rectangle

Square square=new Square(4.5);

square.getarea();

square.getperimeter();

}

}

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output

If you have any query please let me know first i will give resolution