String中的方法

        String s1="abcdefgh";
        char[] s2={‘1‘,‘2‘,‘3‘};
        s1.getChars(1, 3, s2, 0);
        System.out.print(s2);

//输出"bc3"

        String s1="abcdefgh";
        char[] s2={‘1‘,‘2‘,‘3‘};
        s1.getChars(1, 3, s2, 1);
        System.out.print(s2);
//输出"1bc"
          

　　　　　String s1="abcdefgh";
        String s2="abcde";
        String s3="c";
        System.out.println(s1.compareTo(s2));//3:s1.length()-s2.length()    8-5=3
        System.out.println(s1.compareTo(s3));//-2:‘a‘-‘c‘
        System.out.println(s3.compareTo(s1));//2:‘c‘-‘a‘

　　　　　String s1="abcdefgh";
        String s2="Abcde";
        String s3="C";
        System.out.println(s1.compareToIgnoreCase(s2));//3:s1.length()-s2.length()    8-5=3
        System.out.println(s1.compareToIgnoreCase(s3));//-2:‘a‘-‘c‘
        System.out.println(s3.compareToIgnoreCase(s1));//2:‘c‘-‘a‘

        String s1="abcdefgh";
        System.out.println(s1.startsWith("c",2 ));//true
        System.out.println(s1.startsWith("cd",2 ));//true
        System.out.println(s1.startsWith("cde",2 ));//true
        System.out.println(s1.startsWith("ce",2 ));//false
        System.out.println(s1.startsWith("a"));//true
        System.out.println(s1.startsWith("ab"));//true
        System.out.println(s1.startsWith("b"));//false        

        String s1="abcdefga";
        System.out.println(s1.indexOf(97));//97是‘a‘  返回0
        System.out.println(s1.indexOf(98));//98是‘b‘  返回1
        System.out.println(s1.indexOf(99));//99是‘c‘  返回2
        System.out.println(s1.indexOf(105));//105是‘i’，，，没出现
        System.out.println(s1.indexOf("d"));//返回3
        System.out.println(s1.indexOf("a",7));//返回7        

　　　　　String s1="abcdefga";
        System.out.println(s1.replace(‘a‘, ‘d‘));//  "dbcdefgd"
        System.out.println(s1.replace("ab", "#"));//   "#cdefga"
        System.out.println(s1.replaceAll("[a-z]", "#"));//   "########"

    String s1="1a2b3c4d5e6f7g8a";
        String[] res=s1.split("[a-z]");
        for(String item:res){
            System.out.println(item);
        }
        //res={"1","2","3","4","5","6","7","8"}

 System.out.println(String.format("%f", 100.0));//100.000000默认六位
    System.out.printf("%f %n", 100.0);    //100.000000