What are the differences between StringBuffer and StringBuilder in Java

This article mainly talks about "what are the differences between StringBuffer and StringBuilder in Java". Interested friends may wish to have a look. The method introduced in this paper is simple, fast and practical. Now let the editor take you to learn "what are the differences between StringBuffer and StringBuilder in Java?"

Let's first look at the class structure of StringBuffer and StringBuilder:

In fact, it is very simple to inherit an abstract string parent class: AbstractStringBuilder. Let's take a look at their three differences.

Difference 1: thread safety

StringBuffer: thread safe, StringBuilder: thread unsafe. Because all exposed methods of StringBuffer are synchronized-decorated, while StringBuilder is not StringBuilder-decorated.

StringBuffer code snippet:

@ Override public synchronized StringBuffer append (String str) {toStringCache = null; super.append (str); return this;}

Difference 2: buffer

StringBuffer code snippet:

Private transient char [] toStringCache; @ Override public synchronized String toString () {if (toStringCache = = null) {toStringCache = Arrays.copyOfRange (value, 0, count);} return new String (toStringCache, true);}

StringBuilder code snippet:

@ Override public String toString () {/ / Create a copy, don't share the array return new String (value, 0, count);}

As you can see, every time StringBuffer fetches toString, it directly uses the toStringCache value of the cache to construct a string.

StringBuilder, on the other hand, needs to copy the character array and construct a string each time.

So, cache flushing is also an optimization of StringBuffer, but the toString method of StringBuffer is still synchronous.

Difference 3: performanc

Since StringBuffer is thread-safe, all its exposed methods are synchronized, and StringBuilder does not synchronize methods, there is no doubt that StringBuilder performs much better than StringBuffer.

Summary

Therefore, StringBuffer is suitable for scenarios where multithreading is used to operate the same StringBuffer, and StringBuilder is more suitable for single-thread scenarios.

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