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<>char type
* stay Java in char（2 Bytes ） Type describes UTF-16 A unit of code in coding , Unless you really have to deal with it UTF-16 Code unit , It is best to treat strings as abstract data types
<> character string （String）（StringBuffer and StringBuilder To be added ）
*
Java That's the string Unicode Character sequence ,Java There is no built-in string type , It's about standards Java A predefined class is provided in the library , be called “String”, Its instances are enclosed in double quotation marks
for example String e = " "; // An empty string String greeting = "Hello"; <>String Common methods in computer
* substring（）
effect ： Extract a substring from a larger string
for example ： String greeting = "Hello"; String s = greeting.substring(0,3);
// After calling the method ,s="Hel", Only the location is extracted 3 previous , Namely （0,1,2）（ Excluding location 3） Of , Its length is also very easy to calculate ,len=3-0=3.
* “+” Splicing
Java Language allowed “+” Join two strings , It should be noted that , If it is a string and non string connection , The latter is converted to a string （ stay Java in , Any string can be converted to a string ）
for example ：
example 1. Common splicing
String expletive = "Expletive"; String PGL3 = "deleted"; String message =
expletive+ PGL3; //message = Expletivedeleted
example 2. String splicing with other types
int a = 13; String name = "name" + a; // The results are as follows "name13"
example 2 The feature of is applied to the output statement , We often use it
*
equals（）
effect ： Can be used to detect whether two strings are equal （ content ）, For example, expressions ：
s.equal(t)
If string s And string t equal , Then return true, Otherwise, return false.
be careful ： Don't use it == Detects whether two strings are equal , This operator can only detect whether two strings are placed in the same position
*
length（）
effect ： Returns the length of the string
String greeting = "Hello"; int n = greeting.length(); // Count Reg 5
image String.charAt(int index), The unit of code that can be returned to that location ,String There are many useful ways , For more information, please check API
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