Java · Theory

StringBuffer in Java

Theory

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StringBuffer in Java

StringBuffer is a mutable text builder. append, insert, reverse change the same object. Methods are synchronized — safer if two threads share it, a bit slower.

In a single-thread student program, StringBuilder is usually the better pick. Use StringBuffer when the buffer is shared across threads.

Don’t build a long string with + in a loop. Use append.

Let's take this on the board with one tiny Main class — no extra files. StringBuffer in Java — same append idea as Builder, but synchronized. Start from main, go line by line, and stop at each print. That output is the proof for StringBuffer.

Exam tip

Mutable + synchronized. Prefer StringBuilder unless two threads share it.

Example

// StringBuffer demo
public class Main {
  public static void main(String[] args) {
    StringBuffer sb = new StringBuffer("Hi");
    sb.append(" Java");
    System.out.println(sb);
  }
}

StringBuffer in Java — same append idea as Builder, but synchronized.

Short notes

DefStringBuffer = mutable text. append changes the same object.
RuleMethods are synchronized (thread-safe, slower).
UseShared across threads. One thread → StringBuilder.
Trap+ in a loop instead of append.

Java · Theory

StringBuffer in Java

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Theory

79/270

StringBuffer in Java

StringBuffer is a mutable text builder. append, insert, reverse change the same object. Methods are synchronized — safer if two threads share it, a bit slower.

In a single-thread student program, StringBuilder is usually the better pick. Use StringBuffer when the buffer is shared across threads.

Don’t build a long string with + in a loop. Use append.

Exam tip

Mutable + synchronized. Prefer StringBuilder unless two threads share it.

Example

// StringBuffer demo
public class Main {
  public static void main(String[] args) {
    StringBuffer sb = new StringBuffer("Hi");
    sb.append(" Java");
    System.out.println(sb);
  }
}

StringBuffer in Java — same append idea as Builder, but synchronized.

Short notes

DefStringBuffer = mutable text. append changes the same object.
RuleMethods are synchronized (thread-safe, slower).
UseShared across threads. One thread → StringBuilder.
Trap+ in a loop instead of append.

StringBuffer in Java

Example

Short notes

Questions

StringBuffer in Java

Example

Short notes

Questions