Java-StringBuffer and StringBuilder classes

string buffers

StringBuffer class

When learning the string class, the API says that the string buffers support variable strings, what is a string buffer? Next we'll look at the string buffers.

Lookup StringBuffer's Api,stringbuffer, also known as the variable character sequence , is a string-like buffer that can be changed by some method calls to the length and content of the sequence.

The original stringbuffer is a string buffer, that is, it is a container , the container can be loaded with a lot of strings. and the ability to perform various operations on the strings.

the StringBuffer method uses

Code Demo:

Creates a string buffer object. Used to store data.

StringBuffer sb = new StringBuffer ();

SB.Append("haha"); Add a String

SB.Insert(2, "it");//insert at specified location

sb.Delete(1, 4);//delete (front closed rear open)

SB.Replace(1, 4, "cast");//replace the content within the specified range (front-closed)

　　String str = sb.tostring ();

Note: After the Append, delete, insert, replace, and reverse method calls, the return value is the current object itself , so stringbuffer it can change the length and content of the character sequence .

method chaining calls to Objects

In our development, we encounter the case of returning an object after invoking a method. It then uses the returned object to continue calling the method. This time, we can put the code together now, like the Append method, the code is as follows:

Creates a string buffer object. Used to store data.

StringBuffer sb = new StringBuffer ();

Add data. After constantly adding data, to manipulate the last data of the buffer, it must be converted to a string.

String str = Sb.append (True). Append ("hehe"). ToString ();

StringBuffer Practice

Exercise: int[] arr = {34,12,89,68}; Convert elements in a int[] to string format [34,12,89,68]

Public Static String tostring_2 (int[] arr) {

StringBuffer sb = new stringbuffer ();

Sb.append ("[");

for (int i = 0; i < arr.length; i++) {

if (i!=arr.length-1) {

Sb.append (arr[i]+ ",");

}Else{

Sb.append (arr[i]+ "]");

}

}

return sb.tostring ();

}

No matter how much data, what type of data is not important, as long as the end becomes a string can use StringBuffer this container

StringBuilder class

The Lookup API Discovery also has a StringBuilder class, which is also a string buffer, what is the difference between StringBuilder and StringBuffer?

We read the API description of StringBuilder and found that it is also a variable sequence of characters. This class provides an API that is compatible with StringBuffer, but does not guarantee synchronization. This class is designed to be used as a simple replacement for stringbuffer, which is common when a string buffer is used by a single thread. If possible, it is recommended that this class be preferred because, in most implementations, it is faster than StringBuffer .

Java-StringBuffer and StringBuilder classes