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command line options

Command Line Argument:-value supplied to the main method String array from the run time or from command prompt called command line argument. All the values will be String. When we supplied value from command prompt automatically an array will be created of that length (number of arguments).
Example1:- Command.java
class Command
{
public static void main(String[]args)
{
System.out.println("Demo of Command Line");
}
}
Output:-
C:\JAVATECH>javac Command.java
C:\JAVATECH>java Command command com om
Demo of Command Line
Example2:- Command.java
class Command
{
public static void main(String[]args)
{
System.out.println("Demo of Command Line");
System.out.println(args[0]);
}
}
Output:-
C:\JAVATECH>javac Command.java
C:\JAVATECH>java Command command com om
Demo of Command Line
Command
Example3:- Command.java
class Command
{
public static void main(String[]args)
{
System.out.println("Demo of Command Line");
System.out.println(args[0]);
System.out.println(args[1]);
System.out.println(args[2]);
}
}
Output:-
C:\JAVATECH>javac Command.java
C:\JAVATECH>java Command command com om
Demo of Command Line
command
com
om
Example4:- Command.java
class Command
{
public static void main(String[]args)
{
System.out.println("Demo of Command Line");
System.out.println(args[0]);
System.out.println(args[1]);
System.out.println(args[2]);
}
}
Output:-
C:\JAVATECH>javac Command.java
C:\JAVATECH>java Command 101 102 Hello
Demo of Command Line
101
102
Hello
Example5:- Command.java
class Command
{
public static void main(String[]args)
{
System.out.println("Demo of Command Line");
System.out.println(args[0]+args[1]+args[2]);
}
}
Output:-
C:\JAVATECH>javac Command.java
C:\JAVATECH>java Command 101 102 Hello
Demo of Command Line
101102Hello
Example6:- Command.java
class Command
{
public static void main(String[]args)
{
System.out.println("Demo of Command Line");
for(int i=0;i<args.length;i++)
{
System.out.println(args[i]);
}
}
}
Output:-
C:\JAVATECH>javac Command.java
C:\JAVATECH>java Command 101 102 Hello
Demo of Command Line
101
102
Hello
Example7:- Command.java
class Command
{
public static void main(String[]args)
{
System.out.println("Demo of Command Line");
for(int i=0;i<args.length;i++)
{
System.out.println(args[i]);
}
}
}

Output:-
C:\JAVATECH>javac Command.java
C:\JAVATECH>java Command "101 102 Hello" 500 700
Demo of Command Line
101 102 Hello
500
700
Example8:-Command.java
class Command
{
public static void main(String[]args)
{
int s=0;
System.out.println("Demo of Command Line");
for(int i=0;i<args.length;i++)
{
System.out.println(args[i]);
s=s+Integer.parseInt(args[i]);
}
System.out.println("total sum="+s);
}
}
Output:-
C:\JAVATECH>javac Command.java
C:\JAVATECH>java Command 101 102 100
Demo of Command Line
101
102
100
total sum=303
Example9:-Command.java
class Command
{
public static void main(String[]args)
{
int s=0;
System.out.println("Demo of Command Line");
for(int i=0;i<args.length;i++)
{
System.out.println(args[i]);
s=s+Integer.parseInt(args[i]);
}
System.out.println("total sum="+s);
}
}
Output:-
C:\JAVATECH>java Command 101 102 100h
Demo of Command Line
101
102
100h
Exception in thread "main" java.lang.NumberFormatException: For input string: "1
00h"
        at java.lang.NumberFormatException.forInputString(Unknown Source)
        at java.lang.Integer.parseInt(Unknown Source)
        at java.lang.Integer.parseInt(Unknown Source)
        at Command.main(Command.java:10)
Example10:-Command.java
class Command
{
public static void main(String[]args)
{
System.out.println("Demo of Command Line");
System.out.println(args[0]);
}
}
Output:-
C:\JAVATECH>javac Command.java
C:\JAVATECH>java Command
Demo of Command Line
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 0
        at Command.main(Command.java:6)
Array:-Array is special type of variable which can store multiple values into a single variable but all the values must be same. In java array is object.
How to use array:-
1.     Declaration of array
2.     Create array
Syntax for array declaration:-
type arrayname[];
Or
type []arrayname;
For example
int a[];  or
int[]a;
Create array:-
a=new int[5];  or
int a[]=new int[5];
or
int []a=new int[5];
Example1:ArraY.java
class ArraY
{
public static void main(String[]args)
{
int []a;
a=new int[5];
System.out.println("length of array is : "+a.length);
}
}
Output:-
C:\JAVATECH>javac ArraY.java
C:\JAVATECH>java ArraY
length of array is : 5
Example2:- ArraY.java
class ArraY
{
public static void main(String[]args)
{
int []a;
a=new int[5];
System.out.println("length of array is : "+a.length);
System.out.println("Array elements are : ");
for(int i=0;i<a.length;i++)
{
a[i]=i+2;
System.out.println(a[i]);
}
}
}
Output:-
C:\JAVATECH>javac ArraY.java
C:\JAVATECH>java ArraY
length of array is : 5
Array elements are :
2
3
4
5
6
Example3:-ArraY.java
class ArraY
{
public static void main(String[]args)
{
int []a={10,20,30,40,50,60,70,80};
System.out.println("length of array is : "+a.length);
System.out.println("Array elements are : ");
for(int i=0;i<a.length;i++)
{
System.out.print(a[i]);
}
}
}
Output:-
C:\JAVATECH>javac ArraY.java
C:\JAVATECH>java ArraY
length of array is : 8
Array elements are :

10 20 30 40 50 60 70 80
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