The for Statement

The 

for statement provides a compact way to iterate over a range of values. Programmers often refer to it as the “for loop” because of the way in which it repeatedly loops until a particular condition is satisfied. The general form of the 

for statement can be expressed as follows:

for (initialization; termination; increment) { statement(s) }

When using this version of the 

for statement, keep in mind that:

• The initialization expression initializes the loop; it’s executed once, as the loop begins.
• When the termination expression evaluates to 

false, the loop terminates. - The increment expression is invoked after each iteration through the loop; it is perfectly acceptable for this expression to increment or decrement a value.

The following program, [

ForDemo](https://docs.oracle.com/javase/tutorial/java/nutsandbolts/examples/ForDemo.java), uses the general form of the 

for statement to print the numbers 1 through 10 to standard output: ```java class ForDemo { public static void main(String[] args){ for(int i=1; i<11; i++){ System.out.println(“Count is: “ + i); } } }

The output of this program is:

Count is: 1 Count is: 2 Count is: 3 Count is: 4 Count is: 5 Count is: 6 Count is: 7 Count is: 8 Count is: 9 Count is: 10 ``` Notice how the code declares a variable within the initialization expression. The scope of this variable extends from its declaration to the end of the block governed by the 

for statement, so it can be used in the termination and increment expressions as well. If the variable that controls a 

for statement is not needed outside of the loop, it’s best to declare the variable in the initialization expression. The names 

i, 

j, and 

k are often used to control 

for loops; declaring them within the initialization expression limits their life span and reduces errors.

The three expressions of the 

for loop are optional; an infinite loop can be created as follows:

// infinite loop for ( ; ; ) {

// your code goes here }

The 

for statement also has another form designed for iteration through Collections and arrays This form is sometimes referred to as the enhanced for statement, and can be used to make your loops more compact and easy to read. To demonstrate, consider the following array, which holds the numbers 1 through 10:

int[] numbers = {1,2,3,4,5,6,7,8,9,10};

The following program, [

EnhancedForDemo](https://docs.oracle.com/javase/tutorial/java/nutsandbolts/examples/EnhancedForDemo.java), uses the enhanced 

for to loop through the array: ```java class EnhancedForDemo { public static void main(String[] args){ int[] numbers = {1,2,3,4,5,6,7,8,9,10}; for (int item : numbers) { System.out.println(“Count is: “ + item); } } }

In this example, the variable 

item holds the current value from the numbers array. The output from this program is the same as before:

Count is: 1 Count is: 2 Count is: 3 Count is: 4 Count is: 5 Count is: 6 Count is: 7 Count is: 8 Count is: 9 Count is: 10 ``` We recommend using this form of the 

for statement instead of the general form whenever possible. ## The while and do-while Statements

The 

while statement continually executes a block of statements while a particular condition is 

true. Its syntax can be expressed as:

while (expression) { statement(s) }

The 

while statement evaluates expression, which must return a 

boolean value. If the expression evaluates to 

true, the 

while statement executes the statement(s) in the 

while block. The

while statement continues testing the expression and executing its block until the expression evaluates to 

false. Using the 

while statement to print the values from 1 through 10 can be accomplished as in the following [

WhileDemo](https://docs.oracle.com/javase/tutorial/java/nutsandbolts/examples/WhileDemo.java) program: java class WhileDemo { public static void main(String[] args){ int count = 1; while (count < 11) { System.out.println("Count is: " + count); count++; } } } You can implement an infinite loop using the 

while statement as follows: java while (true){ // your code goes here } The Java programming language also provides a 

do-while statement, which can be expressed as follows: java do { statement(s) } while (expression); The difference between 

do-while and 

while is that 

do-while evaluates its expression at the bottom of the loop instead of the top. Therefore, the statements within the 

do block are always executed at least once, as shown in the following [

DoWhileDemo](https://docs.oracle.com/javase/tutorial/java/nutsandbolts/examples/DoWhileDemo.java) program: java class DoWhileDemo { public static void main(String[] args){ int count = 1; do { System.out.println("Count is: " + count); count++; } while (count < 11); } }