Data Structure --- Java --- String, StringBuilder, StringBuffer

1 Overview

　　　　　　1.1 String: string immutable

public final class String implements java.io.Serializable, Comparable<String>, CharSequence {
    

     // final of the array of characters
        private final char value[];

}    

　　

　　　　　　1.2　　the StringBuilder : strings can be changed, not thread safe

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

    // call the parent class constructor, and then call your own append method
     public StringBuilder(String str) {
        super(str.length() + 16);
        append(str);
    }

    @Override
    public StringBuilder append(Object obj) {
        return append(String.valueOf(obj));
    }

}    

　　

abstract class AbstractStringBuilder implements Appendable, CharSequence {
    

      
       char[] value;


       AbstractStringBuilder(int capacity) {
          value = new char[capacity];
       }

}    

　　

　　

　　　　　　　　　  StringBuffer : strings can be changed, thread-safe

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


    // call the parent class constructor, then call their append method
     public StringBuffer(String str) {
        super(str.length() + 16);
        append(str);
    }


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

}