Java-string,stringbuilder,stringbuffe type Use

1,string class

1.1 Definition :

    Stringclass represents a string. All string literals (such as) in a Java program "abc" are implemented as instances of this class.

strings are constants , and their values cannot be changed after they are created. A string buffer supports variable strings. Because String

Objects are immutable, so they can be shared. For example:

String s1= "ABC";

String s2= "ABC";//Because ABC is constant, so Java no longer opens up new space, so

S1 and S2 point to the same "ABC", that is, S1==s2 is true. and string S3=new string ("abc");

The S3 points to an object, which points to "ABC".

1.2 Construction methods

String (byte[] bytes);//The character that corresponds to the value of bytes.

String (char[] value);//consists of a char character array

string (char[],offset,count): Converts a portion of a character array into a string.

String (string original);

String (StringBuilder builder);

String (stringbuffer buffer);

1.3 Member methods

1, get

    1.1 contains the number of characters in the string, which is the length of the string.
         int length (): Gets the length.
    1.2 gets the position of a character based on its location.
          char charAt (int index): index is the subscript position of the string.
    1.3 gets the character in the string position based on the character.
         int indexOf (int ch): Returns the position of the first occurrence of the corresponding character of CH in the string. CH can be changed to char ch.
         int indexOf (int ch, int FromIndex): Gets the position where Ch appears in the string, starting at the specified position in FromIndex.

int indexOf (String str): Returns the position of the first occurrence of STR in a string.
int indexOf (string str, int fromIndex): Gets the position where Str appears in the string, starting at the specified position fromIndex.

int lastIndexOf (int ch):

2, Judge.
2.1 Whether a substring is contained in a string.
Boolean contains (str):
Special: IndexOf (str): The first occurrence of STR can be indexed if 1 is returned. Indicates that the STR does not exist in the string.
Therefore, it can also be used to determine whether the specified is included. if (str.indexof ("AA")!=-1) and the method can be judged,

There are locations where you can get the occurrences.

whether there is content in 2.2 characters.
boolean isEmpty (): The principle is to determine whether the length is 0.
2.3 Whether the string starts 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 string contents are the same. The Equals method in the object class is replicated.
Boolean equals (str);
2.6 Determine if the content is the same and ignore the case.
boolean equalsignorecase ();

3, Convert.
3.1 Converts a character array into a string.
Constructor: String (char[])
String (Char[],offset,count): Converts a portion 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 Converts a string into a character array.
Char[] ToCharArray ():

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

3.4 Converts a string into a byte array.
Byte[] GetBytes ():
3.5 Convert the base data type to a string.
static String valueOf (int)
Static String valueOf (double)

"";//string.valueof (3);

Special: Strings and byte arrays can be specified in the encoding table during the conversion process.

3.5, replace
String replace (Oldchar,newchar);

3.6, cutting
String[] Split (regex);

3.7, sub-string. Gets the part of the string.
String substring (begin);
String substring (begin,end);

3.8, convert, remove spaces, compare.
3.8.1 the string to uppercase or lowercase.
String toUpperCase ();
String toLowerCase ();

3.8.2 removes multiple spaces at both ends of a string.
String trim ();

3.8.3 a natural order comparison of two strings.
int CompareTo (string);

Returns 0 only if two strings are the same. The remainder returns the ASSII code difference of their different characters, which is the positive negative number.

Java-string,stringbuilder,stringbuffe type Use