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This article mainly shows you the "sample analysis of String StringBuffer, StringBuilder and String in java", which is easy to understand and well-organized. I hope it can help you solve your doubts. Let the editor lead you to study and study the "sample analysis of String StringBuffer, StringBuilder and String in java".

Variability

To put it simply: the String class uses the final keyword modifier character array to hold the string, private final char value [], so the String object is immutable. Both StringBuilder and StringBuffer inherit from the AbstractStringBuilder class, and in AbstractStringBuilder an array of characters is used to hold the string char [] value but not modified with the final keyword, so both objects are mutable.

The constructors of StringBuilder and StringBuffer are implemented by calling the parent constructor, that is, AbstractStringBuilder, and you can consult the source code on your own.

Thread safety

Objects in String are immutable, which can be understood as constants and thread-safe. AbstractStringBuilder is the common parent of StringBuilder and StringBuffer, defining some basic string operations, such as expandCapacity, append, insert, indexOf and other public methods. StringBuffer adds a synchronization lock to a method or a synchronization lock to a called method, so it is thread-safe. StringBuilder does not add a synchronization lock to the method, so it is not thread-safe.

Performance

Each time a change is made to the String type, a new String object is generated, and the pointer is then pointed to the new String object. Instead of generating a new object and changing the object reference, StringBuffer operates on the StringBuffer object itself each time. In the same case, using StringBuilder can only get a performance improvement of about 10% to 15% compared with using StringBuffer, but it runs the risk of multi-thread unsafety.

Summary of the use of the three:

Manipulate a small amount of data: suitable for String

Manipulate a large amount of data under a single-thread string buffer: suitable for StringBuilder

Multithreaded operation string buffer to manipulate a large amount of data: suitable for StringBuffer

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