Quick introduction to Java Programming language - Part 1

It is also known as Condition Statements. These statements are used to execute some instruction at specific condition.

Types of Condition Statements are:

• if
• else
• else if
• switch

The “if”statement:

This statement consists of an expression which results in Boolean value true/false.

Syntax:

if(condition)
{
   //statements
}

Example:

public class IfDemo
{
	public static void  main(String[] args) 
		{
		int i=0;
		System.out.println("Before increment i value is: "+i);
		if(i>=0)
		   {
			i++;
		 }
		System.out.println("After increment i value is: "+i);
	}
}

Output:

The “if...else”Statement:

This statement is used to execute false part when the Boolean expression is false.

Syntax:                                                                                                                                     

if(condition)
{
        //statements if condition is true
}
else
{
        //statements if condition is false
}

Example

public class IfElseDemo
{
    public static void  main(String[] args) 
   {
        int i=0;
       System.out.println("Main starts");
	if(i>=1)
	   {
		System.out.println("if part:condition is true");
	   }
	else
	  {
		System.out.println("Else part: condition is false");
	  }
	System.out.println("Main Ends");
   }
}

Output

The “else if” Statement:

This statement is used to put more than one condition.The if statement can be followed by an else if...else statement if necessary,

Syntax:

If(condition)
{
       //statements
}
else
{
        //statements
}
else if
{
       //statement
}

Example: 

public class  Account 
{
	public static void  main(String[] args) 
		{
		int testMarks = 91;
		int rank =0;

		if (testMarks>= 90) {
			rank = 1;
		} else if (testMarks>= 80) {
			rank = 2;
		 } else if (testMarks>= 70) {
			rank = 3;
		 } else {
			rank = 11;
		 }
		System.out.println("Rank is: " + rank);
	   }
}

 Output

The switch Statement:

It is used to evaluate the list of values.

• To come out from each case use break, if there is no break also no error in java.
• If necessary then we can add break depends on requirement.
• There is no order for case you can write default at the beginning only and default is optional.

• Case values must be unique get the value from expected and matched with all cases if match execute the statement or else execute default.

Syntax:

switch(variable)
{
 case value1: 
       statements;
 break;
 case value2: 
       statements;
 break;
                     .
                     .
                     .
 default: 
       statement;
 break;
}

Example

public class SwitchDemo
 {
	public static void  main(String[] args) 
	{
		int n=2;

		switch(n)
			  {
		case 1 :
		System.out.println("Sunday"); 
		break;
		case 2 :
			System.out.println("Monday"); 
			break;
		case 3 :
		System.out.println("Tuesday");
		break;
		case 4 :
		System.out.println("Wednesday");
		break;
		case 5 :
		System.out.println("Thursday");
		break;
		case 6 :
		System.out.println("Friday");
			break;
		case 7 :
			System.out.println("Saturday");
			break;
		default :
		System.out.println("Invalid day");
			  }
		System.out.println("day is: " + n);
	}
}

 Output