String类中常用方法总结【二】

package com.bjsxt.wrap;


public class TestStringMehtods {

        public static void main(String[] args ) {

                byte [] b ={97,98,99};

               System. out .println( new String( b ));   //byte[]---->String

                /**(1)byte [] getBytes()*/

               String str = "helloworld" ;   //String -->byte[] 

                byte [] buf = str .getBytes();

                for ( byte by : buf ){

                       System. out .println( by );

               }

               /*(2) int indexOf( int /String)   int indexOf( int /String , int fromIndex)*/

               System. out .println( str .indexOf(101)); // 在索引为 1 的位置上，找到返回索引

               System. out .println( str .indexOf( 'l' )); // 自动类型转换 char--> int    2,

               System. out .println( str .indexOf( "e" ));

               System. out .println( str .indexOf( "e" ,3)); //-1 找不到返回 -1

               

                /**(3) int lastIndexOf( int /String)   int lastIndexOf( int /String, int fromIndex)*/

               System. out .println( str .lastIndexOf( 'o' ));   //o 最后一次出现的位置  6

               System. out .println( str .lastIndexOf( 'o' ,3)); //-1

               System. out .println( str .lastIndexOf( "o" , 7)); //6 

                /**(4)boolean isEmpty() 字符串的长为 0 时 -- 》 true*/

               System. out .println( "" .isEmpty());

               String s = null ;

                //System.out.println(s.isEmpty());

               

                /**(5)replace(char oldchar ,char newchar )   replace(CharSequence c,CharSequence c2)*/

               System. out .println( str );

                str = str .replace( 'o' , ' 中 ' );   // 使用 " 中 " 替换所有的 'o'

               System. out .println( str );

               /**(6)String [] split(String s)  1998-8-9*/

               String sDate = "1998-8-9" ;

               String [] ss = sDate .split( "-" );

                for (String string : ss ) {

                       System. out .println( string );

               }

                /**(7)CharSequence subSequence( int startIndex, int endIndex)*/

               CharSequence sss = str .subSequence(2, 5); // 含头不含尾

               System. out .println( sss ); // 调用了 toString 方法

                // 如何将 CharSequence 转 String   -->toString()

                /**(8)String subString( int startIndex, int endIndex)*/

                str = str .substring(2, 5); // 含头不含尾

               System. out .println( str );

               

                /**(9)char []toCharArray()*/

                char [] c = str .toCharArray();

               System. out .println( " 数组的长度 :" + c . length );

                for ( char d : c ) {

                       System. out .println( d );

               }

               /**(10)String trim()*/

               String strr = "   hello   world   " ;

               System. out .println( strr .length());

                strr = strr .trim();

               System. out .println( strr + strr .length());

               

                /**(11)staticString valueOf( 任意类型 )*/

               String s1 =String. valueOf (12);

               String s2 =String. valueOf ( true );

               String s3 =String. valueOf ( new char []{ 'a' , 'b' });

               String s4 =String. valueOf ( new Integer(12)); // 进行了向上类型转换，转成了 Object 类型  Object obj =new Integer(12);

       }

}