1. Character arrays and strings.
A string can be converted into a character array. Similarly, a character array can be converted into a character string.
The following operations are provided in the string class.
1) convert the string into a character array: Public char [] tochararray ();
2) character array to string: Public String (char [] value)
Public String (char [] value, int offset, int count); // represents the Count characters starting from the offset position, and is combined into a string.
Public class stringapidemo01 {public static void main (string ARGs []) {string str1 = "hello"; // defines the string char C [] = str1.tochararray (); // convert a string to a character array for (INT I = 0; I <C. length; I ++) {// cyclically output system. out. print (C [I] + ",");} system. out. println (""); // wrap string str2 = new string (c); // convert all character arrays to string str3 = new string (C ); // convert some character arrays to string system. out. println (str2); // output string system. out. println (str3); // output string }}
Running result:
H, E, l, l, O
Hello
El
The preceding two methods are used: String-to-array and array-to-string.
2. Extract the characters at the specified position from the string.
If you want to perform this operation, the return type must be char.
Usage: Public char charat (INT index)
Public class stringapidemo02 {public static void main (string ARGs []) {string str1 = "hello"; // defines the string object system. out. println (str1.charat (3); // retrieves the fourth character from the string }};
Output result:
L
3. String and bety array conversion.
Byte array, which is often used in I/O
In the string class, the following methods are provided to convert strings and byte arrays.
1) string to byte array: Public byte getbytes ();
2) Change a byte array to a string:
Convert all arrays into strings: Public String (byte [] Byte );
Convert some arrays into strings: Public String (char [] Byte, int offset, int count );
Public class stringapidemo03 {public static void main (string ARGs []) {string str1 = "hello"; // defines the string byte B [] = str1.getbytes (); // convert the string to the byte array system. out. println (new string (B); // convert all byte arrays to the string system. out. println (new string (B, 1, 3); // convert part of the byte array to a string }};
4. Obtain the length of an array.
Public int length ();
Public class stringapidemo04 {public static void main (string ARGs []) {string str1 = "Hello lixinghua"; // defines the string variable system. out. println ("\" "+ str1 +" \ ":" + str1.length ());}};
5. Check whether the specified string exists.
In practice, it is often used to determine whether a string contains certain content. You can use the following method:
1) search from the beginning: Public int indexof (string Str); returns the subscript starting with the string.
2) search from the specified position: Public int indexof (string STR, int fromindex); // return an int data, indicating the specific position of the string. If not, -1,
Public class stringapidemo05 {public static void main (string ARGs []) {string str1 = "abcdefgcgh"; // declare the string system. out. println (str1.indexof ("C"); // find the returned location system. out. println (str1.indexof ("C", 3); // query the return position, starting from 4th. out. println (str1.indexof ("X"); // No-1} is returned }};
Running result:
2, 7,-1
6. Remove spaces.
Trim () can remove spaces between the left and right sides of the string, but spaces in the middle of the string cannot be removed.
Public class stringapidemo06 {public static void main (string ARGs []) {string str1 = "hello"; // defines the string system. out. println (str1.trim (); // output after spaces are removed }};
Running result:
Hello
Seven, character truncation.
To extract part of the content from a string, use the following method:
1) truncate from the specified position to the last position; Public string substring (INT beginindex );
2) intercept the content of the specified range: Public string substring (INT beginindex, int endindex );
Public class stringapidemo07 {public static void main (string ARGs []) {string str1 = "Hello World"; // defines the string system. out. println (str1.substring (6); // captures the system from the first position. out. println (str1.substring (); // intercept 0 ~ Content in five locations }};
Running result:
World
Hello
8. Split the string.
If you want to split a string by the specified string, use: Public String [] Split (string RegEx)
Public class stringapidemo08 {public static void main (string ARGs []) {string str1 = "Hello World"; // defines the string s [] = str1.split (""); // split string by space (INT I = 0; I <S. length; I ++) {// cyclically output system. out. println (s [I]) ;}}
Running result:
Hello
World
The example is split into two strings by space to form a string array containing two strings.
9. case-sensitive conversion.
Convert all uppercase strings to lowercase: Public String touppercase ();
Converts all lowercase strings to University: Public String tolowercase ();
Public class stringapidemo09 {public static void main (string ARGs []) {system. out. println ("Convert \" Hello world \ "to uppercase:" + "Hello World ". touppercase (); system. out. println ("Convert \" Hello world \ "to lowercase:" + "Hello World ". tolowercase ());}
Running result:
Hello World
Hello word
10. Determine whether to start or end with a specified string.
You can use the following methods in string.
1) whether to start with a specified string: Public Boolean starswith (string prefix)
2) Whether to end with a specified string: Public Boolean endwith (string suffix)
Public class stringapidemo10 {public static void main (string ARGs []) {string str1 = "** hello"; // defines the string str2 = "Hello **"; // define the string if (str1.startswith ("**") {// determine whether the system starts. out. println ("(** Hello) starts with **");} If (str2.endswith ("**") {// determines whether the system ends. out. println ("(Hello **) ended ");}}};
Running result:
(** Hello) starts **
(Hello **) ends **
11. case-insensitive string comparison.
public boolean equalsIgnoreCase(String anotherString)
Public class stringapidemo11 {public static void main (string ARGs []) {string str1 = "hello"; // defines the string str2 = "hello"; // defines the string system. out. println ("\" Hello \ "equals \" Hello \ "" + str1.equals (str2); system. out. println ("\" Hello \ "equalsignorecase \" Hello \ "" + str1.20.signorecase (str2); // case-insensitive comparison }};
Running result:
False
Ture
12. Replace the string.
Use this method to complete string replacement:
Public String replaceall (string RegEx, string replacement );
Public class stringapidemo12 {public static void main (string ARGs []) {string STR = "hello"; // defines the string newstr = Str. replaceall ("L", "x"); // replace all l with X system. out. println ("result after replacement:" + newstr );}};
Running result:
Result After replacement: hexxo
Common Methods of the string class.