Core JAVAWrite Once, Run Anywhere |
There may be a situation when we need to execute a block of code several number of times, and is often referred to as a loop. Java has very flexible three looping mechanisms. You can use one of the following three loops:
As of java 5 the enhanced for loop was introduced. This is mainly used for Arrays.
While Loop
A while loop is a control structure that allows you to repeat a task a certain number of times.
Syntax
The syntax of a while loop is:
When executing, if the boolean_expression result is true then the actions inside the loop will be executed. This will continue as long as the expression result is true. Here key point of the while loop is that the loop might not ever run. When the expression is tested and the result is false, the loop body will be skipped and the first statement after the while loop will be executed.
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do...While Loop
A do...while loop is similar to a while loop, except that a do...while loop is guaranteed to execute at least one time.
Syntax
Notice that the Boolean expression appears at the end of the loop, so the statements in the loop execute once before the Boolean is tested.
If the Boolean expression is true, the flow of control jumps back up to do, and the statements in the loop execute again. This process repeats until the Boolean expression is false.
Example
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for Loop
A for loop is a repetition control structure that allows you to efficiently write a loop that needs to execute a specific number of times. A for loop is useful when you know how many times a task is to be repeated.
Syntax
The syntax of a for loop is:
Here is the flow of control in a for loop:
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Enhanced for loop in Java
As of java 5 the enhanced for loop was introduced. This is mainly used for Arrays.
Syntax
The syntax of enhanced for loop is:
Example
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Break Keyword
The break keyword is used to stop the entire loop. The break keyword must be used inside any loop or a switch statement.
The break keyword will stop the execution of the innermost loop and start executing the next line of code after the block.
Syntax
Example
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continue Keyword
The continue keyword can be used in any of the loop control structures. It causes the loop to immediately jump to the next iteration of the loop.
Syntax
Example
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