Common usage Summary of string in Java _java

1> get

1.1: The number of characters contained in the string, which is the length of the string .
int length (): Get length

1.2: Get a character from the position according to the position.
char charAt (int index)

1.3: Gets the position of the character in the string according to the character.
int indexOf (int ch): Returns the position in which CH first appears in the string.
int indexOf (int ch,int fromindex): Gets the position that CH appears in the string, starting at the Fromindex specified position.

int indexOf (String str): Returns the position in which Str appears for the first time in a string.
int indexOf (String str,int fromindex): Gets the position that STR appears in the string, starting at the Fromindex specified position.

1.4:int LastIndexOf (String str): Reverse indexing.

2> judgment

2.1: Whether a string contains a substring.
Boolean contains (str);
Special: IndexOf (str): You can index STR for the first occurrence, and if you return-1, that STR is not present in the string.
Therefore, it can also be used to determine whether the specified is contained.
if (Str.indexof ("a")!=1)

Moreover, the method can be used to judge or obtain the position that appears.

2.2: There is content in the string.
Boolean IsEmpty (): The principle is to determine whether the length is 0.

2.3: Whether the string begins with the specified content.
Boolean startswith (str);

2.4: Whether the string ends with the specified content.
Boolean endsWith (str);

2.5: Determines whether the character content is the same, and the Equals method in the object class is overwritten.
Boolean equals (str);

2.6: Determine whether the content is the same and ignore case.
Boolean.equalsignorecase ();

3> Conversion

3.1: Converts a character array into a string.
Constructor: String (char[])
String (Char[],offset,count): Converts a part of a character array into a string
static method:
Static String copyvalueof (char[]);
Static String copyvalueof (char[] data,int offset,int count);

Static String valueof (char[]);

3.2: Turn the string into a character group
Char[] ToCharArray ();

3.3: Converts a byte array into a string.
String (byte[])
String (Byte[],offset,count): Converting a portion of a byte array into a string

3.4: Converts a string into a byte array.
Byte[] GetBytes ()

3.5: Turn the base data type into a string,
static String valueof (int)
Static String valueof (double)

3+ "" is the same as the value of string.valueof (3)
Special: Strings and byte arrays can be encoded during conversion.

4> replacement
String replace (Oldchar,newchar);

5> Cutting
String[] Split (regex);

6> substring. Gets the part of the string
String subString (begin);
String subString (begin,end);

7> conversion, remove spaces, compare.

7.1: Turn the string into uppercase or lowercase
String touppercsae () Large-turn small
String tolowercsae () Small Turn large

7.2: Remove multiple spaces at both ends of the string
String trim ();

7.3: A natural order comparison of two strings
int CompareTo (string);

See the following code, which is for one by one examples of the above string seven usages:

Copy Code code as follows:

Class Stringmethoddemo


{


public static void Method_zhuanhuan_qukong_bijiao ()


{


String s = "Hello Java";





The print result is: (There are spaces between Hello and Java front and back doors) Hello Java


SOP (S.touppercase ());

The print result is: (There are spaces between Hello and Java front and back doors) Hello Java
SOP (S.tolowercase ());

Print and result: "Hello Java" with no spaces
SOP (S.trim ());

The upper case of the comparison, the print result is: 1, because B corresponds to the ASCII value is 98,
A corresponds to 97, so b-a=1
String S1 = "abc";
String s2 = "AAA";
SOP (S1.compareto (S2));

}

public static void Method_sub ()
{
String s = "abcdef";

The print result is: Cdef, starting at the specified position to the end. If the corner mark does not exist, the string angle appears out of bounds.
SOP (S.substring (2));

The result is a CD that contains a header and does not contain a tail.
SOP (S.substring (2,4));
}
public static void Method_split ()
{
String s = "Zhangsan,lisi,wangwu";

string[] arr = S.split (",");

for (int x=0; x<arr.length; x + +)
{
SOP (Arr[x]);
}
}

public static void Method_replace ()
{
String s = "Hello java";

String S1 = s.replace (' A ', ' n ');
String S1 = s.replace (' W ', ' n '); If the character you want to replace does not exist, return the original string

String S1 = s.replace ("java", "World");//print Result: Hello World

SOP ("s=" +s); The print result is: Hello Java because once the string is initialized, the value cannot be changed
SOP ("s1=" +s1);//print Result: Hello JNVN

}

public static void Method_trans ()
{
Char[] arr = {' A ', ' B ', ' C ', ' d ', ' e ', ' f '};

string s = new string (arr,1,3);

SOP ("s=" +s);//print Result: BCD

String S1 = "ZXCVBNM";
char[] CHS = S1.tochararray ();

for (int x=0; x<chs.length; x + +)
{
SOP ("Ch=" +chs[x]);//print Result: ch=z,x,c,v,b,n,m
}
}

public static void Method_is ()
{
String str = "Arraydemo.java";

Determine if the file name is the beginning of the array word
SOP (Str.startswith ("Array"));

Determine if the file name is a. java file
SOP (Str.endswith (". Java"));

Determine if the file contains a demo
SOP (Str.contains ("Demo"));
}

public static void Method_get ()
{
String str = "ABCDEAKPF";

Length
SOP (Str.length ());

Get characters from index
SOP (Str.charat (4));
SOP (Str.charat (40)), Stringindexoutofboundsexception (String Corner-crossing exception) occurs when a corner mark that does not exist in the string is accessed

Get an index from a character
SOP (Str.indexof (' a '));
SOP (Str.indexof (' A ', 3));//printing is 5, because the corner Mark 3 is D,
So start looking at a, and the 5th corner is a.
SOP (Str.indexof (' t ', 3)) Print:-1, if no corner mark is found, return-1

Reverses the position in which a character appears (from the right to the left, but the angle or start from the left)
SOP (Str.lastindexof ("a"));
}

public static void Main (string[] args)
{
Method_zhuanhuan_qukong_bijiao ();
Method_sub ();
Method_split ();
Method_replace ();
Method_trans ();
Method_is ();
Method_get ();
/*
String S1 = "abc";
String s2 = new String ("abc");

String s3 = "ABC";
System.out.println (S1==S2);
System.out.println (S1==S3);
*/
}

public static void Sop (Object obj)
{
System.out.println (obj);
}
}