In Java, about string types, random verification codes, time types

One, String type: String type

Define a string

String a= "Hello World"; String b= new String ("Hello World");

Concatenation between strings:

String A=ABCD; String B=ABCD; String  c=a+b; System.out.println (c);//The value of the output is "ABCDABCD"      //string type can also be spliced with int type, assuming int d= 555, then     String e=a+d;  then output E, The obtained value is "abcd555";

Some of the common things about strings:

String  sc= "ABCDEFG"; Sc.length ();       Take the length of the string Sc.indexof (c);    Gets the position of the first occurrence of a character, and the returned value is an int of type   C that represents the found character  . It  is important to note that the obtained value requires +1, which is the position of the character, and in the computer, the index of string is starting from 0 sc.lastindexof (c)  //Gets the position of the last occurrence of a character sc.substring (A, B)     / /intercept string, from A to Bsc.trim ()         //Remove only the front and back spaces of the string, without removing the middle sc.replace (      A, B)//Replace All, replaced by a Bsc.replacefirst (A, B)   // The same is replaced, but only once Sc.equals (b)            //string is compared to each other  whether SC equals b  Returns a value of TRUE or Falsesc.split (,)      //splits the string according to certain rules  "," every time a comma is met, a split

　　

Get data examples with Sc.indexof ():

String s= "<student><xm> Zhang San </xm><xb> male </xb></student>"; int A=s.indexof ("<xm > ");             Locate the first occurrence of the string and assign the value to aint b=s.indexof ("</xm>"), int c=s.indexof ("<xb>"), int d=s.indexof ("</xb>"); String XM = s.substring (a+4, b);    Because we want to take the value after the character, so we have to skip 4 characters and  +4  intercept from a+4 to b;string XB = s.substring (c+4,d);       The reasons are as above, interception from C+4 to D;  System.out.print ("+xm+", Gender "+XB");      Output

　

Random number or letter or letter + digital mixed Verification Code

String a= new String ("1234567890abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ");   The string yzm= "" is specified first;  for (int i=1;i<=4;i++) {int sj= (int) ((Math.random () *100)%a.length ());       The random number in the For loop, and the length of the string, the random digit is a position in the string c=a.substring (SJ, sj+1);                       Intercepts the character of a position in a string, to the character +1yzm=yzm+c;                            The character stitching}   System.out.print (YZM);                 

　　

Second, Time type: Date type

Get Time:

Two methods: 1. Single access, final stitching

Create Calenar Object Calendar a=calendar.getinstance ();//give value int b= a.get (calendar.year) for month and day respectively; int c= a.get (calendar.month) +1 ;     

2, the Calenar format

Create Calenar Object Calendar a= calendar.getinstance ();//Format Time SimpleDateFormat b=new SimpleDateFormat (yyyy-mm-dd hh:mm:ss) ;//to Calender formatted string c= B.format (A.gettime ());//Output System.out.print (c);

　　

In Java, about string types, random verification codes, time types