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Get Started: Java While Loop

In This Article, You Will Learn about Java While Loop.

Java Booleans – Before moving ahead, let’s know a bit about Java Switch.

Table of Contents

Loops

Loop executes to a block of code as long as a specified condition is met.

Loop is majorly used to reduce the lines of code, to make code easy to write, read & understand, and save time & eliminate errors.

Java While Loop

The while loop iterate through a block of code as long as a specified condition is true:

Syntax

				
					while (condition) {
  // code block to be executed
}
				
			

Example: Use the while loop to loop from the number 10 to 1.

				
					public class Main {
  public static void main(String[] args) {
    int i = 10;
    while (i > 0) {
      System.out.println(i);
      i--;
    }  
  }
}
				
			

Note: Do not forget to decrease the value of the variable used in the condition; otherwise, the loop will never stop.

In the example above, the code in the loop will run, over and over again, as long as a variable (i) is 1.

Explanation – 

i = 10,
Then, deduct the 1 from 10, which becomes 9.

Again, 

i = 9,
Then, deduct the 1 from the 9, which becomes 8.

Again, 

i = 8,
Then, deduct the 1 from the 8, which becomes 7, and so on….

Over and again, now the last step

i = 1,
Then, deduct the 1 from 1, which becomes 0,

Now i = 0, since i > 0 (0 > 0) is not true; therefore it breaks the loop and come out of the loop.

Example: Use the while loop to loop from the number 0 to 6.

				
					public class Main {
  public static void main(String[] args) {
    int i = 0;
    while (i < 6) {
      System.out.println(i);
      i++;
    }  
  }
}
				
			

Note: Do not forget to increment the value of the variable used in the condition; otherwise, the loop will never stop.

In the example above, the code in the loop will run, over and over again, as long as a variable (i) is less than 6.

At starting, i = 0,
In the next step, condition is checked (0 < 6),

Since the condition is true; therefore, it executes the number 0,

Then, increment the 0 from 1, which becomes 1.

This procedure will continue until i = 6 ( 6 < 6 ) and the condition goes false, stopping the Loop.

Do/While Loop

Do/While is another type of Loop. This Loop will execute once before the condition is checked; then, it will repeat the Loop as long as it is true.

Syntax

				
					do {
  // code block to be executed
}
while (condition);
				
			

Example: Use the Do/While loop to loop from the number 10 to 1.

				
					public class Main {
  public static void main(String[] args) {
    int i = 10;
    do {
      System.out.println(i);
      i--;
    }
    while (i > 0);  
  }
}
				
			

Note: Do not forget to decrease the value of the variable used in the condition; otherwise, the loop will never stop.

The example above uses a do/while loop. The loop will consistently execute at least once, whether true or false because the code block is executed before the condition is tested.

Explanation – 

At starting, i = 10,
In the next step, execute number 10

Then, deduct the 1 from 10, which becomes 9.

Now checked condition, since ( 9 > 0), it means the state is true; therefore, it repeats the same procedure repeatedly until i = 0, and the condition goes false, which stops the loop.

Example: 

				
					public class Main {
  public static void main(String[] args) {
    int k = 0;
    do {
      System.out.println(k);
      k++;
    }
    while (k < 10);  
  }
}
				
			

Note: Do not forget to increase the value of the variable used in the condition; otherwise, the loop will never stop.

The example above uses a do/while loop. The loop will consistently execute at least once, whether true or false because the code block is executed before the condition is tested.

Explanation – 

At starting, k = 0,
In the next step, execute the number 0

Then, increment the 1 to 0, which becomes 1.

Now checked condition, since ( 1 < 10) it means the state is true; therefore, it repeats the same procedure repeatedly until k = 10, and the condition goes false, which stops the loop.

If you find anything incorrect in the above-discussed topic and have further questions, please comment below.

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