JDK源码阅读--StringBuffer

 

 

public final class StringBuffer
extends AbstractStringBuilder
implements java.io.Serializable, CharSequence


1 /**
2      * A cache of the last value returned by toString. Cleared
3      * whenever the StringBuffer is modified.
4      */
5     private transient char[] toStringCache;//被transient修饰,表示这个字段不被序列化



StringBuffer是被final修饰的,表示不能被其它类继承,;继承了AbstractStringBuilder抽象类,实现了Serializable、CharSequence接口

StringBuffer中的方法被public修饰的都使用了synchronized,保证线程安全。所以StringBuffer是线程安全的类。

 

 1 /**
 2      * Constructs a string buffer with no characters in it and an
 3      * initial capacity of 16 characters.
 4      */
 5     public StringBuffer() {
 6         super(16);
 7     }
 8 
 9     /**
10      * Constructs a string buffer with no characters in it and
11      * the specified initial capacity.
12      *
13      * @param      capacity  the initial capacity.
14      * @exception  NegativeArraySizeException  if the {@code capacity}
15      *               argument is less than {@code 0}.
16      */
17     public StringBuffer(int capacity) {
18         super(capacity);
19     }
20 
21     /**
22      * Constructs a string buffer initialized to the contents of the
23      * specified string. The initial capacity of the string buffer is
24      * {@code 16} plus the length of the string argument.
25      *
26      * @param   str   the initial contents of the buffer.
27      */
28     public StringBuffer(String str) {
29         super(str.length() + 16);
30         append(str);
31     }

 

StringBuffer的容量默认是16,当容量不够的时候,容量会继续增加16,依次类推。

 

posted @ 2019-03-05 09:36  以前、以后  阅读(238)  评论(0编辑  收藏  举报