Example 1 (using if/else statements)

Problem: The program  should check if input is integer and return error if input is greater than 15.

Scanner in=new Scanner(System in);
if (in.hasNextInt())
	{
		int input=in.nextInt();
		if(input==1)
		{...}
		else if(input==2)
		{...}
		else if(input==3)
		{..}
		else
		{System.out.println("error")}
           
	}

else
	{
		System.out.println("not an Integer: " + in.next());
	}



Example 2 (The same problem but with use of switch):

Scanner in=new Scanner(System in);
if (in.hasNextInt())
	{
		int input=in.nextInt();
		switch(input)
		{
			case 1: {...}; break;
			case 2: {...}; break;
			...
			default {error}
		}
           
	}

else
	{
		System.out.println("not an Integer: " + in.next());
	}



Example 3 (Another implementation of input):

Scanner in=new Scanner(System in);
String input = in.next();
if(input.matches("(0)*+[0-9]{1,10}"))
{
	int IntInput=Integer.parseInt(input);
	...
}

else
System.out.println("error");


Example 4 (Using Arrays):

Scanner in=new Scanner(System in);
String input = in.next();

char[]a=input.toCharArray();
for(int i=0; i<a.length;i++)
{
	if(!(Character.isDigit(a[i])))
	{
		System.out.println("error");
	}
	else
	//parse
}