Common Methods of the string class.

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.