Switch Statement

Source: TestSwitch.java


import java.util.Scanner;

public class TestSwitch {

public static void main(String[] args) {

Scanner scan = new Scanner(System.in);

System.out.println("Enter month number");

int monthNumber = scan.nextInt();

switch (monthNumber) {

case 1: System.out.println("JAN");

break;

case 2 : System.out.println("FEB");

break;

case 3 : System.out.println("MAR");

break;

case 4 : System.out.println("APR");

break;

default :

System.out.println("Invalid Month");

}

}

}

User Interaction (Getting Users' Input)

Source: TestUserInput.java

import java.util.Scanner;

public class TestUserInput {

public static void main(String[] args) {

Scanner scan = new Scanner(System.in);

System.out.println("Enter your Name : ");

String name = scan.next();

System.out.println("Enter your marks : ");

int marks = scan.nextInt();

if (marks > 90) {

System.out.println("Hi " + name + " You got A");

} else if (marks > 70) {

System.out.println("Hi " + name + " You got B");

} else if (marks > 50) {

System.out.println("Hi " + name + " You got C");

} else {

System.out.println("Sorry Dude better luck next time");

}

}

}

Mechanism of Method Execution

When we run TestApp5 application, the JVM start the execution by calling main() method of TestApp5.

Command: 

java TestApp5

Execution Model:

Array

- Use to store multiple "elements" together, represented by single variable name
- Need to specify size while declaration, size = total number of elements
- Element can be accessed using array "index"
- Array index starts from zero [0]


======================================================
Ex. 1: Array of int (primitive data type)

Source: TestArray1.java

public class TestArray1 {

    public static void main(String[] args) {
     
        int[ ] ilist = new int [10];
        ilist[0] = 101;
        ilist[7] = 200;
     
        for(int k = 0; k < ilist.length; k++ ) {
            System.out.println(ilist[k]);
        }
    }
}

Output: 
101
0
0
0
0
0
0
200
0
0
======================================================
Ex. 2: Array of float (primitive data type)

Source: TestArray2.java

public class TestArray2 {


    public static void main(String[] args) {
       
        float[] ilist = new float [10]; // size
        ilist[0] = 101.50;
        ilist[7] = 200.25;
       
        for(int k = 0; k < ilist.length; k++ ) {
            System.out.println(ilist[k]);
        }
    }
}

Output: 
101.50
0.0
0.0
0.0
0.0
0.0
0.0
200.25
0.0
0.0
======================================================
Ex. 3: Array of String (reference data type)

Source: TestArray3.java

public class TestArray3 {

   public static void main(String[] args) {
     
   String[] weekdays = new String[7]; // size
        weekdays[0] = "Monday";
        weekdays[1] = "Tuesday";
        weekdays[2] = "Wednesday";
        weekdays[3] = "Thursday";
        weekdays[4] = "Friday";
        weekdays[5] = "Saturday";
        weekdays[6] = "Sunday";
      
        for(int k = 0; k < weekdays.length; k++ ) {
            System.out.println(weekdays[k]);
        }
    }
}

Output: 
Monday
Tuesday
Wednesday
Thursday
Friday
Saturday
Sunday

Command Line Arguments

With command line arguments it is possible to send configuration information to the application. 

Source: TestArgument.java

public class TestArgument {

         public static void main(String[] args) {        

            int size = Integer.valueOf(args[0]);

            int[] list = new int[size]; 
            System.out.println("Size of the array= " + list.length);           

}

     }

Output: Size of the array=25

Run:

java TestArgument  25

Syntax:

java  ProgramName  argument1  argument2  argumentN