javaj basis (String and StringBuilder --- immutable and mutable sequence of characters using traps)

String：

　　StringClass represents character strings. All string literal Java program (e.g. "abc") are implemented as an instance of this class.

　　Strings are constant; their values ​​can not be changed after creation. String buffer supports variable strings. Because String objects are immutable, so you can share.

StringBuilder/StringBuffer:

　　A variable sequence of characters. Stringbuilder unsafe, but fast (common), StringBuffer safe and slow.

 

　Use String string splicing :( do not recommend consuming time and space)

　　Example:

　　String str = "";

　　for (int i = 0; i <5000; i ++) {
　　　　STR STR + = i;   equivalent to 10,000 objects generated object i, str an object

　　}

　Use StringBuilder for string splicing:

　　StringBuilder str = new StringBuilder("");

　　for(itn i = 0;i < 5000;i++){

　　　　str.append (i);  save a lot of time and space

　　}