Java Chuanjiang How string objects are defined

How do I define a string object? string s = "abc"; The data that is caused by double quotation marks is a string object.

features : Once the string is initialized, it cannot be changed and stored in a constant pool in the method area. Because the string class is final decorated

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String S1 = "abc";//S1 there is only one object in memory pointing to ABC.

string s2 = new String ("abc");//s2 There are two object ABC, new in the point .

System.out.println (S1==S2);//false

System.out.println (s1.equals (S2));//true , equals in the string compares the contents of the strings.

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Method of String:

1 : Constructor method: converts a byte array or an array of characters into a string.

string S1 = new string ();//A string that creates an empty content.

String s2 = Null;//s2 does not have any object pointing, it is a null constant value.

string s3 = "";//s3 points to a specific string object, except that there is no content in the string.

// generally, when you define a string, you do not need new.

String S4 = new String ("Java video");

String S5 = "Java video"; This is commonly used in this notation

new String (char[]);// converts a character array into a string.

new String (Char[],offset,count);// converts a portion of a character array into a string.

2 : General method:

According to the idea of object-oriented:

2.1 Get:

2.1.1: Gets the length of the string. length ();

2.1.2: The character at the specified position. Char charAt(int index);

2.1.3: Gets the position of the specified character. If there is no return-1, you can use the return value-one to determine if a character does not exist.

int indexOf(int ch);//Returns the first-time character corner label

int indexOf (int ch,int fromIndex); Returns the first time a corner label was found at the beginning of the specified position

int indexOf (String str); Returns the first string corner label found

int indexOf (String str,int fromIndex);

int lastIndexOf(int ch);

int lastIndexOf (int ch,int fromIndex);

int lastIndexOf (String str);

int lastIndexOf (String str,int fromIndex);

2.1.4: Gets the substring.

String substring(int start);//starting at the start bit, up to length ()-1.

String substring (int start,int end);//from Start to end. Contains the start bit, and does not contain an end bit.

SUBSTRING (0,str.length ());//Get the whole string

2.2 Judgment:

2.2.1: Does the string contain the specified string?

Boolean contains(String substring);

2.2.2: Does the string start with the specified string?

Boolean startsWith(string);

2.2.3: Does the string end with the specified string?

Boolean EndsWith (string);

2.2.4: Determine if strings are the same

Boolean equals(string);//Overrides the method in object to determine whether the contents of the string are the same.

2.2.5: Determines whether the string contents are the same, ignoring case.

Boolean equalsignorecase(string);

2.3 Conversion:

2.3.1: You can convert a character array or a byte array into a string by using a constructor function.

2.3.2: You can convert a character array to a string by using a static method in the string.

Static String copyvalueof(char[]);

Static String copyvalueof (Char[],int offset,int count);

Static String valueOf(char[]);

Static String valueOf (Char[],int offset,int count);

2.3.3: Converts the base data type or object into a string.

Static String valueOf (char);

Static String ValueOf (Boolean);

Static String valueOf (double);

Static String valueOf (float);

static String valueOf (int);

Static String valueOf (long);

Static String valueOf (Object);

2.3.4: Turns the string to case.

String tolowercase();

String touppercase();

2.3.5: Converts a string to an array.

Char[] tochararray();//turn into a character array.

Byte[] getBytes();//Can be added to the encoding table. Turns into a byte array.

2.3.6: Converts a string into an array of strings. Cutting method.

String[] split(split rule-string);

2.3.7: Replace the string with the content. Note: Changing to a new string does not modify the original string directly.

String Replace(Oldchar,newchar);

String replace (oldstring,newstring);

2.3.8: string concat(string);//Append to Strings.

String trim();//remove spaces at both ends of the string

int compareTo();//If the argument string equals this string, the value 0 is returned, or if the string is less than the string parameter in dictionary order, a value less than 0 is returned if the string is larger than the string parameter in dictionary order , a value greater than 0 is returned .

Java Chuanjiang How string objects are defined