Detailed explanation of controlling output line spacing and flow control statements in Java nested loops

This tutorial explains in detail how to implement line spacing control in Java nested loops to produce clear formatted output. We'll look at ways to achieve extra line breaks using `System.lineSeparator()` and double `System.out.println()`, and show how to avoid trailing empty lines. In addition, the article will also briefly explain the role of `break` and `continue` statements in loops to help beginners better master loop control skills.

Java Nested Loops and Basic Output

In Java programming, nested loops are a common structure when dealing with two-dimensional data structures or scenarios that require multiple iterations. The following is a typical nested for loop example, which prints out a sequence of multiples of 6, with the number of numbers increasing in each line:

 public class Main {
  public static void main(String[] args) {
    for (int i = 1; i <p> The output of this code is a line break immediately after the end of each line of numbers, with no additional blank lines between lines:</p><pre class="brush:php;toolbar:false"> 6 
6 12 
6 12 18 
...

Implement line spacing control

To make the output more readable by adding extra blank lines between each line of output, we can modify the newline logic.

Method 1: Use System.lineSeparator()

System.lineSeparator() is a recommended practice because it returns the correct line separator according to the current operating system (for example, \n for Linux/Unix, \r\n for Windows), thus ensuring code consistency across different platforms.

 public class Main {
  public static void main(String[] args) {
    for (int i = 1; i <p> <strong>Output result:</strong></p><pre class="brush:php;toolbar:false"> 6 

6 12 

6 12 18 

6 12 18 24 

6 12 18 24 30 

6 12 18 24 30 36 

6 12 18 24 30 36 42 

6 12 18 24 30 36 42 48 

6 12 18 24 30 36 42 48 54 

6 12 18 24 30 36 42 48 54 60 

6 12 18 24 30 36 42 48 54 60 66 

6 12 18 24 30 36 42 48 54 60 66 72 

6 12 18 24 30 36 42 48 54 60 66 72 78

Method 2: Call System.out.println() twice

This is a more direct method but may not be as flexible as System.lineSeparator(). Simply calling System.out.println() twice can achieve the same effect.

 public class Main {
  public static void main(String[] args) {
    for (int i = 1; i <h3> Avoid trailing blank lines</h3><p> The above method adds extra blank lines after all lines, including the last line. If you want to avoid an extra blank line at the end of the entire output, you can add a conditional to the outer loop.</p><pre class="brush:php;toolbar:false"> public class Main {
  public static void main(String[] args) {
    for (int i = 1; i <h3> Loop control statements: break and continue</h3><p> In addition to the basic loop structure, Java also provides break and continue statements to more finely control the execution flow of the loop.</p><h4> break statement</h4><p> The break statement is used to immediately terminate the innermost loop (for, while or do-while), jump out of the loop body, and continue executing the code after the loop.</p><p> <strong>Example: Early termination in inner loop</strong></p><p> Suppose we want to print each line only up to the number 30 (i.e. 6 * j does not exceed 30).</p><pre class="brush:php;toolbar:false"> public class Main {
  public static void main(String[] args) {
    for (int i = 1; i  30) { // If the current number exceeds 30, terminate the inner loop break; 
        }
        System.out.print(6 * j " ");
      }
      System.out.println(System.lineSeparator());
    }
  }
}

Partial output:

 6 

6 12 

6 12 18 

6 12 18 24 

6 12 18 24 30 

6 12 18 24 30 
...

Starting from the sixth line, since 6 * j will exceed 30, the inner loop will terminate early.

continue statement

The continue statement is used to skip the remaining code in the current loop iteration and immediately proceed to the next iteration. It does not terminate the entire loop.

Example: Skip specific values ​​in inner loop

Let's say we want to skip printing the number 18 (i.e. 6 * j == 18).

 public class Main {
  public static void main(String[] args) {
    for (int i = 1; i <p> <strong>Partial output:</strong></p><pre class="brush:php;toolbar:false"> 6 

6 12 

6 12 24 

6 12 24 30 

6 12 24 30 36 
...

As you can see, all rows 18 are skipped.

Summary and Notes

• Line spacing control: The most recommended way to achieve line spacing is to use System.out.println(System.lineSeparator()); because of its cross-platform compatibility. Calling System.out.println() twice directly is also a viable alternative.
• Avoid blank lines at the end: By adding a conditional judgment (if (i
• break and continue:
  • break is used to completely exit the current loop.
  • continue is used to skip the remainder of the current loop iteration and go directly to the next iteration.
• Readability: Although break and continue provide powerful loop control capabilities, excessive use of them may complicate the code logic and reduce readability. When designing loops, clear and concise logic should be prioritized.
• Coding style: Good code indentation and comments are crucial to understanding nested loops and control-flow statements, especially in the beginning stages.

Mastering these techniques will help you better control loop behavior and output formats in Java programs, and write more robust and user-friendly applications.

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