Common methods of the string class

1. String and character

Method name	Method type	Method description
Public String (char[] value)	Construction method	Converts the specified array of characters into a string
Public String (char[] value,int offset,int count)	Construction method	Converts a character array of a specified range into a string
public char charAt (int index)	Common methods	Gets the character at the specified position within the string
Public Char ToCharArray ()	Common methods	To change a string into a character array

Example: The character that gets the specified index position

public class Demo

{

public static void Main (string[] args) {

String str = "Hello world";

Char c =str.charat (2);

System.out.println (c);

}

}

Example: manipulating strings to and from character arrays

public class Demo

{

public static void Main (string[] args) {

String str = "Hello";

char[] data = Str.tochararray ();//Converts a string into a character array

for (int i =0;i<data.length;i++) {

Data[i]-= 32;

}

System.out.println (new String (data));

}

}

Example : Give a string that asks whether the string is composed of numbers.

public class Demo

{

public static void Main (string[] args) {

String msg = "235468841";

System.out.println (Isnumber (msg));

}

public static Boolean isnumber (String str) {

char[] data = Str.tochararray ();//Converts a string into a character array

for (int i=0;i<data.length;i++) {

if (data[i]> ' 9 ' | | data[i]< ' 0 ') {

return false;

}

}

return true;

}

}

2. Strings and bytes

Method name	Method type	Method description
Public String (byte[] bytes)	Construction method	Change a byte array to a string
Public String (byte[] bytes,int offset,int length)	Construction method	Converts a byte array of a specified range into a string
Public byte[] GetBytes ()	Common methods	Changing a string into a byte array
Public byte[] GetBytes (String charname)	Common methods	Encoding Conversion

Example:Implementing string-to-byte conversions

public class Demo{public static void Main (string[] args) {string msg = "HelloWorld"; byte data[] = Msg.getbytes ();//change String to byte Array for (int i=0;i<data.length;i++) {System.out.println (data[i]);d ata[i]-= 32;} System.out.println (); System.out.println (new String (data));}}

3. String comparisons

Method name	Method type	Method description
public boolean equals (String str)	Common methods	Determines whether two strings are equal (case sensitive)
public boolean equalsignorecase (String str)	Common methods	Determines whether two strings are equal (case insensitive)
public int compareTo (String str)	Common methods	Compare uppercase relationships of two strings

Example: observing two types of string comparisons

public class demo{

public static void Main (string[] args) {

String msg = "HelloWorld";

String msgb= "HELLOWORLD";

System.out.println (Msg.equals (MSGB));//false

System.out.println (Msg.equalsignorecase (MSGB));//true

}

}

4. String Lookup

Method name	Method type	Method description
Public boolean contains (String str)	Common methods	Determine if a string exists
public int indexOf (String str)	Common methods	Finds the position of the specified character from scratch, returns the position of the specified character if found, otherwise, returns 1
public int indexOf (String str,int fromIndex)	Common methods	The position is returned by the specified position by the front and back, if found, returns the location of the character, otherwise, 1
public int lastIndexOf (String str)	Common methods	Finds the position of the specified character from the back forward
public int lastIndexOf (String str,int fromIndex)	Common methods	From the specified position, from the back forward to find the location
public boolean startsWith (String prefix)	Common methods	Determines whether to start with the specified string
public boolean startsWith (String prefix,int toffset)	Common methods	Starts at the specified position to determine whether to start with the specified string
public boolean endsWith (String suffix)	Common methods	Determines whether to end with the specified string

Example: using contains () query

public class demo{

public static void Main (string[] args) {

String str = "Hello world";

if (Str.contains ("Hello")) {

SYSTEM.OUT.PRINTLN ("The specified string has been found");

}

}

}

5. String substitution

Method name	Method type	Method description
public string ReplaceAll (string regex,string replacement)	Common methods	Full replacement
public string Replacefirst (string regex,string replacement)	Common methods	Replace the first

Example: Replace operation

public class demo{

public static void Main (string[] args) {

String str = "Hello world";

System.out.println (Str.replaceall ("L", "_"));

}

}

6. String splitting

Method name	Method type	Method description
Public string[] Split (String regex)	Common methods	Full split
Public string[] Split (String regex,int limit)	Common methods	Split part

Example: implementing a split of IP addresses

public class demo{

public static void Main (string[] args) {

String str = "192.168.1.1";

string[] data = str.split ("\ \");

for (int i =0;i<data.length;i++) {

System.out.println (Data[i]);

}

}

}

7. String interception

Method name	Method type	Method description
Public String substring (int beginindex)	Common methods	Intercept from start position to end
Public String substring (int beginindex,int endIndex)	Common methods	Set Start and End indexes

8. Other methods

Method name	Method type	Method description
public string concat (String str)	Common methods	String connection
Public String Intern ()	Common methods	string into Pool
public boolean isEmpty ()	Common methods	Determines whether an empty string
public int Length ()	Common methods	Get string length
Public String toLowerCase ()	Common methods	Turn lowercase
Public String toUpperCase ()	Common methods	Turn capital
Public String trim ()	Common methods	Remove left and right spaces

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Common methods for string classes