A Sample Class

The Class in Java is an Object Oriented Wrapper that can hold variables and methods. You can think of it as a container (a box). A computer program in Java is made up of 1 or more classes.

Example 1:


import java.util.Scanner;

public class Sample {
        
    // a constructor or initializer
    // a constructor has no return type, not even void
    // a constructor has the same name as the class
    // a constructor is called immediately after new
    // it's purpose is to initialize instance variables
    public Sample() 
    {
	    // code can go here
    }
    
    // the main method is the starting point
    // this is executed when the program is first run
    public static void main(String[] args) 
    {
        // create some local variables
        double m; // holds the slope of the line
        double x; // holds the x value
        double b; // holds the y intercept
        double y; // holds the y value
		
        // create a Scanner object in memory
        // that can read data from the keyboard		 
        Scanner scan = new Scanner (System.in);
		
        System.out.println("The Slope of a Line");
        System.out.println();
        System.out.println();
		
        System.out.print("Enter the slope ");
        m = scan.nextDouble();
        
        System.out.print("Enter the value of x ");
        x = scan.nextDouble();
        
        System.out.print("Enter the value of b ");
        b = scan.nextDouble();
        
        y = m*x + b;
        System.out.println("The value of m is " + m);
        System.out.println("The value of x is " + x);
        System.out.println("The value of m is " + m);
        System.out.println("The value of y is " + y);
    }
}







Example 2:




import java.util.Scanner;

public class Sample2 {
        
    public Sample2() {
    }
    
    public static void main(String[] args) {
        
        Scanner scan = new Scanner (System.in);
        
        System.out.println("Semester Grade");
        System.out.println();
        System.out.println();		

        System.out.print("Enter your semester 1 grade ");
        double s1 = scan.nextDouble();
        System.out.println();
        System.out.print("Enter your semester 2 grade ");
        double s2 = scan.nextDouble();
        System.out.println();
        System.out.print("Enter your final exam grade ");
        double exam = scan.nextDouble();
        System.out.println();
        System.out.println();
        double grade = (s1 + s2) / 2 * .8 + exam * .2;
        System.out.println("Your semester grade is " + grade );
        System.out.println();
        System.out.println();		
    }
}







Example 3:





import java.util.Scanner;

public class Sample3 {
        
    public Sample3() {
    }
    
    public static void main(String[] args) {
        
        Scanner scan = new Scanner (System.in);
        
        System.out.println("Slope of a Line");
        System.out.println();
        System.out.println();
        System.out.print("Enter x1 ");
        double x1 = scan.nextDouble();
        System.out.print("Enter y1 ");
        double y1 = scan.nextDouble();
        System.out.println();
        System.out.print("Enter x2 ");
        double x2 = scan.nextDouble();
        System.out.print("Enter y2 ");
        double y2 = scan.nextDouble();
        System.out.println();
        double slope = (y2-y1)/(x2-x1); // x2!=x1
        System.out.println("The slope of the line is "+slope);
    }
}


Example 4

// The following MyPoint class holds the coordinates
// for a point on a 2D plane.

public class MyPoint {

    // instance variables
    int x;
    int y;
    
    // constructor MyPoint with 2 parameters
    // this.x refers to the instance variable x
    // x refers to the temporary parameter variable x
    public MyPoint(int x, int y)    
    {
        this.x = x; 
        this.y = y;
    }
    
    // other methods not shown
       
}