Kotlin string
Strings are used to store text.
A string contains a collection of characters surrounded by double quotes:
typical example
var greeting = "Hello"
together withJava Unlike a string, you don't have to specify that the variable is a string, and Kotlin is smart enough to understand the double quotes in the above example.greeting The variable is a string.
However, as with other data types, you can specify the type if you insist:
typical example
var greeting: String = "Hello"
Note: If you want to create a string but not assign a value (and assign it later), you must specify the type when you declare the variable:
typical example
That's OK:
var name: String
name = "John"
println(name)
typical example
This creates an error:
var name
name = "John"
println(name)
Access to strings
To access the characters (elements) of a string, the index number must be quoted in square brackets.
The string indexes from the0 Start. In the following example, we access thetxt The first and third elements in the
typical example
var txt = "Hello World"
println(txt[0]) // first element (H)
println(txt[2]) // third element (l)
[0] is the first element.[1] is the second element.[2] It's the third element, and so on.
String length
Strings in Kotlin are objects that contain properties and functions that can perform certain operations on strings by writing a dot character after a specific string variable (.). For example, you can use thelength property finds the length of the string:
typical example
var txt = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
println("The length of the txt string is: " + )
string function
There are many string functions available, such astoUpperCase() cap (a poem)toLowerCase()：
typical example
var txt = "Hello World"
println(()) // exports "HELLO WORLD"
println(()) // exports "hello world"
Compare strings
compareTo(string) function compares two strings, if they are equal then return0：
typical example
var txt1 = "Hello World"
var txt2 = "Hello World"
println((txt2)) // outputs 0 (they are equal)
Find strings within strings
indexOf() function to return to the specified text in the string of the first occurrence of the position (including spaces):
typical example
var txt = "Please locate where 'locate' occurs!"
println(("locate")) // exports 7
Remember, Kotlin counts from zero.
0 is the first position in the string.1 It's the second one.2 It's the third ......
Quotation marks in strings
To use quotes in a string, use single quotes ('）：
typical example
var txt1 = "It's alright"
var txt2 = "That's great"
string concatenation
You can use the+ Operators add them together to form a new string. This is called concatenation:
typical example
var firstName = "John"
var lastName = "Doe"
println(firstName + " " + lastName)
Note that we added an empty text (" ") to print in thefirstName cap (a poem)lastName Creates a space between
You can also use theplus() function joins two strings:
typical example
var firstName = "John "
var lastName = "Doe"
println((lastName))
String templates/interpolation
In addition to concatenation, you can also use "string templates", which are an easy way to add variables and expressions to strings.
Simply use the$ Symbolic references to variables:
typical example
var firstName = "John"
var lastName = "Doe"
println("My name is $firstName $lastName")
"String templates are a popular feature of Kotlin because they reduce the amount of code. For example, you don't have to add a string template to thefirstName cap (a poem)lastName Specify spaces between them.
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