Simple string operations

String

String is a class, not a basic data type.

Method for creating a String object

1. String S = "hello ";

2. String S = new string ("hello ");

3. Char chars [] = {'x', 'y', 'z '};

String S1 = new string (chars );

String S2 = new string (chars, 0, 2 );

"=" And "equals ()"

=: Determines the address of two strings in the memory, that is, whether the string object is the same

Equals ():Check whether the characters that constitute the string are completely consistent

Connection string

1. Use "+"
2. Use Concat ()

String S = new string ("hello ,");

String name = new string ("James! ");

String sentence = S. Concat (name );

System. Out. println (sentence );

Stringbuffer stringbulider

It is used to store and operate variable data consisting of multiple characters and is usually used to dynamically construct character data.

Statement

Stringbuffer ST = new stringbuffer (); // create a null stringbuffer object

Stringbuffer ST = new stringbuffer (10); // create an object with the specified initial length

Stringbuffer ST = new stringbuffer ("AAA"); // create a variable to store the string aaa

Use

St. tostring (); // convert to string type

St. append ("***"); append the string

Differences

Stringbuffer variable string thread security, multithreading

Stringbuilder is the fastest, with a single thread

Example: randomly generate Verification Code

Public class string01 {

Public static void main (string [] ARGs ){

String STR = "abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyz0123456789 ";

Stringbuilder S = new stringbuilder ();

Int Len = 4;

For (INT I = 0; I <= Len; I ++ ){

Random r = new random ();

Int P = R. nextint (Str. Length ());

S. append (Str. charat (p ));

}

System. Out. println (S. tostring ());

 

}

 

}

Randomly generate image names (Based on Time)

Public class string02 {

 

Public static void main (string [] ARGs ){

String fn = "aaa-ffff.jpg ";

String ext = fn. substring (fn. lastindexof ('.'));

String newfile = new simpledateformat ("yyyymmddhhmmsss"). Format (new date () + ext;

String n2 = UUID. randomuuid (). tostring () + ext;

System. Out. println (N2 );

 

}

 

}

// UUID randomly generates a number of strings with different values

// Formatting time simpledateformat ("yyyymmddhhmmsss"). Format (new date ())

Show today's day of the week

Public class string03 {

 

Public static void main (string [] ARGs ){

String week = "day, one, two, three, four, five, six ";

String [] wk = week. Split (","); // splits the string based on the matching of the given regular expression.

// Date d = new date ();

// String n = "today is: Week" + wk [D. getday ()];

Calendar c = calendar. getinstance ();

// System. Out. println (C. Get (calendar. day_of_week ));

String n = "today is: Week" + wk [C. Get (calendar. day_of_week)-1];

System. Out. println (N );

 

}

 

}

Examples of Common Extraction Methods

 

Other string operations

Simple string operations