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Building Text with StringBuilder

StringBuilder is a mutable character buffer for accumulating text across multiple steps. toString produces the final immutable String. Save as Main.java and run with a Java 17+ JDK: java Main.java.

Syntax

new StringBuilder().append(value).append(other).toString()

Examples

Building Text with StringBuilder

Save as Main.java and run with a Java 17+ JDK: java Main.java.

import java.lang.StringBuilder;

public class Main {
  public static void main(String[] args) throws Exception {
    StringBuilder text = new StringBuilder();
    for (int i = 1; i <= 3; i++) {
      if (i > 1) text.append(", ");
      text.append("item-").append(i);
    }
    System.out.println(text.toString());
  }
}
  1. Expected output: item-1, item-2, item-3
  2. The loop adds separators only between items and reuses one buffer throughout the accumulation.

Best practices

  • Prefer ordinary concatenation for short fixed expressions.
  • Do not share a StringBuilder across threads without synchronization.

Runtime & versions

Java Virtual Machine. Feature availability depends on the language and runtime version used by your project; consult the official reference below.

Java Language Specification

Specifications & further reading