The String.indent(int n) method in Java is a useful tool for formatting multi-line strings by adjusting the amount of leading space (indentation) on each line. Introduced in Java 12, it performs the following for the specified n indentation:

1. Positive n: Adds n spaces to the beginning of each line in the string.
2. Negative n: Removes up to n leading spaces from each line.
3. Zero n: Leaves the string unchanged (but trims blank lines at the start/end).

This is particularly useful for formatting text in structured views, like logs, JSON, XML, or pretty-printed output.

Example: Using String.indent to Format Output

Here is how you can use the String.indent() method:

package org.kodejava.lang;

public class StringIndentExample {
    public static void main(String[] args) {
        // Original multi-line string (no indentation)
        String text = "Line 1\nLine 2\nLine 3";

        // Adding an indent of 4 spaces
        String indented = text.indent(4);
        System.out.println("Indented by 4 spaces:\n" + indented);

        // Removing 2 leading spaces (negative indent)
        String negativeIndent = indented.indent(-2);
        System.out.println("Indented with -2 (removing spaces):\n" + negativeIndent);

        // Applying indent to empty lines
        String withEmptyLines = "Line 1\n\nLine 3";
        String indentedWithEmptyLines = withEmptyLines.indent(4);
        System.out.println("Handling empty lines:\n" + indentedWithEmptyLines);
    }
}

Explanation of Code:

1. Adding Indentation: The first call to .indent(4) adds 4 spaces to each line.
2. Removing Indentation: .indent(-2) deducts 2 spaces from the start of each line (if spaces exist).
3. Empty Lines: When dealing with blank lines, indent maintains the level of indentation for such lines, adding or removing spaces as needed.

Output:

Indented by 4 spaces:
    Line 1
    Line 2
    Line 3

Indented with -2 (removing spaces):
  Line 1
  Line 2
  Line 3

Handling empty lines:
    Line 1

    Line 3

Notes:

• Empty lines and their indentation are preserved.
• Lines with no leading spaces are unaffected by negative indentation.
• Leading and trailing full blank lines are removed.

When to Use:

• To format multiline strings cleanly.
• To produce human-readable or formatted output in tools or commands (e.g., logging, text processing).