Java variable character of self-study notes (StringBuffer)

Overview StringBuffer class

StringBufferIs a string variable, he objects can be expanded and modified.
It is thread-safe, mutable sequence of characters.

The difference between StringBuffer and a String

StringIt is an immutable sequence of characters.
StringBufferIs a variable sequence of characters.

StringBuffer class constructor

public final class StringBuffer extends AbstractStringBuilder implements Appendable, Serializable, CharSequence {
	public StringBuffer(){}//无参构造方法
	public StringBuffer(int capacity){
		//指定容量的字符串缓冲区对象
		super(capacity);
	} 
	public StringBuffer(String str){
		//指定字符串内容的字符串缓冲区对象
		super(str)
	}
}

Use StringBuffer methods

public int capacity(): Returns the current capacity. (Theoretical value: know like)
public int length(): Returns the length (number of characters). (Actual value: often used)

• Example:
  StringBuffer stringBuffer = new StringBuffer();创建一个StringBuffer对象
stringBuffer.length();//获取StringBuffer的长度

StringBuffer add functionality

• public StringBuffer append(String str):
  You can be added to any type of data string buffer inside, and returns the string buffer itself.
• public StringBuffer insert(int offset,String string):
  At the specified position to insert any kind of data into a string buffer inside, and returns the string buffer itself.

StringBuffer delete function

• public StringBuffer deleteCharAt(int index):
  Delete the character at the specified location and returns itself.
• public StringBuffer delete(int start,int end):
  Delete the contents of the specified start position from the end of the specified location and returns itself.

StringBuffer replace and reverse function

• StringBuffer replace function
  public StringBuffer replace(int start,int end,String str) //从 start 开始到 end 用 str 替换
• StringBuffer's reverse function
  public StringBuffer reverse() //字符串反转

StringBuffer be intercepted and precautions

• StringBuffer interception function
  public String substring(int start) //从指定位置截取到末尾
public String substring(int start,int end) //截取从指定位置开始到结束位置，包括开始位置，不包括结束位置
• Note: The return value type is no longer StringBuffer itself.

StringBuffer and String interconversion

• = String> the StringBuffer
  1. By constructing method;
  2. append()Method.
• = The StringBuffer> String
  1. By constructing method;
  2. toString(); Method
  3. through subString(0,length).

The array translated into strings

• Demand: the array of data together into a string in the specified format

  public static void main(String[] args){
  	String[] strings = { "a", "b", "c", "d" };
  	StringBuffer stringBuffer = new StringBuffer();
  	for (String string : strings){
  		stringBuffer.append(string);
  	} 
  	System.out.println(stringBuffer.toString());
  }
  

The difference between StringBuffer and StringBuilder

1. StringBuffer String variable (thread-safe)
2. StringBuilderString variable (non-thread-safe)
   java.lang.StringBuildera variable sequence of characters is the new 5.0. This class provides with a StringBuffercompatible API, but does not guarantee synchronization. The class is designed as StringBuffera drop-in replacement string buffer is used when using a single thread (which is common). If possible, we recommend the use of such priority, because in most implementations, it is more than StringBufferfast to. Both methods are substantially the same.

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