Control Statements and Loops

Expression / Statement

An assignment or increment / decrement expression can be made into a statement by adding a semi-colon. An expression statement is executed by evaluating the expression.

Empty Statement

An empty statement does nothing: 
;

if Statement

The if statement allows conditional execution of a statement (with a single if ) or a conditional choice of two statements (with if-else ), executing one or the other but not both. 
if ( Expression )
  Statement
If the Expression evaluates to true, then Statement is executed. If the Expression evaluates to false then nothing happens. 
if ( Expression )
  Statement1
else
  Statement2
If the Expression evaluates to true, then Statement1 is executed. If the Expression evaluates to false then Statement2 is executed.

Switch Statement

The switch statement transfers control to one of several statements depending on the value of an Expression. The type of the Expression must be char, byte, short, int or String. 
switch (k)
{
  case 0:  System.out.println ("zero"); break;
  case 1:  System.out.println ("one"); break;
  default: System.out.println ("out of range"); break;
}
The body of a switch statement is known as a switch block. Any statement immediately contained by the switch block may be labeled with one or more case or default labels. When the switch statement is executed, first the Expression is evaluated. If one of the case constants is equal to the value of the expression, then all the statements after the matching case label in the switch block are executed. If no case matches but there is a default label, then all the statements after the matching default label are executed. If there is a break statement then the switch statement completes execution.

Conditional Operator ? :

The conditional operator ? : uses the boolean value of one expression to decide which of the other two expresions should be evaluated. 
max = ( a > b ) ? a : b;
The first expression must be of type boolean.

while Statement

The while statement executes an Expression and a Statement repeatedly until the value of the Expression is false. The Expression must have type boolean. If the value of the Expression is false the first time it is evaluated, then the Statement is not executed. 
while ( Expression )
  Statement

do Statement

The do statement executes an Expression and a Statement repeatedly until the value of the Expression is false. The Expression must have type boolean. If the value of the Expression is false the first time it is evaluated, then the Statement is executed at least once. 
do
  Statement
while ( Expression );

for Statement

The for statement executes some initialization code, then executes an Expression, a Statement, and some update code repeatedly until the value of the Expression is false. 
for ( Init; Expression; Update )
  Statement
The Init code is a list of statement expressions, the expressions are evaluated in sequence from left to right. If in the Init code, there is a local variable declaration then the scope of the local variable is in the for block. If the value of the Expression is false the first time it is evaluated, then the Statement is not executed.

Labeled Statements

Statements may have label prefixes. 
  Identifier : Statement
The Java programming language has no goto statement. The identifier statement labels are used with break and continue statements.

break

The break transfers control out of an enclosing statement. 
  break Identifier;
The Identifier is optional. If there is an Identifier, then break attempts to transfer control to the statement having the same label as the Identifier.

continue Statement

The continue statement may occur only in a while, do, or for statement. The continue statement ends the current iteration and begins a new one.