JAVA BEGINNERS TUTORIAL – Conditions

Programming is conditions and it is the main core of start writing a code as when you think in any problem you will find that you need to take decision for that we have decision making statments as the following:

The if-then Statement:

An if statement consists of an expression followed by one or more statements. this expression evaluates a boolean result (TRUE or FALSE).

Syntax:

The syntax of an if statement is:

If the expression evaluates to true then the block of code inside the if statement will be executed. If not the first set of code after the end of the if statement (after the closing curly brace) will be executed.

Example:

This would produce the following result:

The if-then-else Statement:

An if statement can be followed by an optional else statement, which executes when the Boolean expression is false.

Syntax:

The syntax of an if…else is:

Example:

The if-then-else if-then-else Statement:

An if statement can be followed by an optional else if…else statement, which is very useful to test various conditions using single if…else if statement.

When using if , else if , else statements there are few points to keep in mind.

  • An if can have zero or one else’s and it must come after any else if’s.
  • An if can have zero to many else if’s and they must come before the else.
  • Once an else if succeeds, none of the remaining else if’s or else’s will be tested.

Syntax:

The syntax of an if…else is:

Example:

The switch Statement:

A switch statement allows a variable to be tested for equality against a list of values. Each value is called a case, and the variable being switched on is checked for each case.

Syntax:

The syntax of enhanced for loop is:

The following rules apply to a switch statement:

  • The variable used in a switch statement can only be a byte, short, int, or char.
  • You can have any number of case statements within a switch. Each case is followed by the value to be compared to and a colon.
  • The value for a case must be the same data type as the variable in the switch and it must be a constant or a literal.
  • When the variable being switched on is equal to a case, the statements following that case will execute until a break statement is reached.
  • When a break statement is reached, the switch terminates, and the flow of control jumps to the next line following the switch statement.
  • Not every case needs to contain a break. If no break appears, the flow of control will fall throughto subsequent cases until a break is reached.
  • A switch statement can have an optional default case, which must appear at the end of the switch. The default case can be used for performing a task when none of the cases is true. No break is needed in the default case.

Example: