使用StringBuilder或StringBuffer拼接字符串,StringBuilder是线程不安全的,StringBuffer是线程安全的//常规写法vark:String = StringBuilder().append("我").append("在").append("学").append("Java").toString();//Lambda表达式写法,函数式编程varl:String = buildString {...
Kotlin中变量用var来标识,var 的全拼是:variable ['vεəriəbl] 2、变量的声明与使用 代码语言:javascript 复制 funmain(args:Array<String>){varname="CnPeng"println(name)} 在上面的代码中,我们通过var name="CnPeng"声明了一个变量name ,并给他赋值 “CnPeng” ,这样,我们再次执行该main函数时,输...
Long数据类型取值范围:[-2^63,2^63-1] ,如果一个数字变量没有标明类型,并且大于2^31-1,或者小于-2^31这个范围,则该变量将为long类型 val distance = 10000000000 // distance variable of type Long 同样,您可以使用大写字母L指定变量的类型Long。例如, val distance = 100L // Long类型的距离值 Double类...
varname:String name="John"println(name) Try it Yourself » Example This will generate an error: varname name="John"println(name) Try it Yourself » Note:You will learn more aboutData Types in the next chapter. Notes onval When you create a variable with thevalkeyword, the valuecannot...
A String in Kotlin is an object, which contain properties and functions that can perform certain operations on strings, by writing a dot character (.) after the specific string variable. For example, the length of a string can be found with the length property:...
interfaceComparable<inT>{operatorfuncompareTo(other:T):Int}fundemo(x:Comparable<Number>){x.compareTo(1.0)// 1.0 has type Double, which is a subtype of Number// Thus, you can assign x to a variable of type Comparable<Double>valy:Comparable<Double>=x// OK!} ...
at variable.VariableKt.main(Variable.kt) 1. 2. 3. VIII . ?= 与 ?. 与 ?: 运算符 1 . ?= 声明可空类型 :? 还有一个作用是声明可空变量 , 此时 ? 修饰符必须在 变量类型之后 ;声明可空类型后 , 可以为其正常赋值 , 也可以为变量赋空值 ; ...
String name; // 默认值是 null int count; // 默认值是 0 但这些 Kotlin 是没有的。不过其实,Java 也只是 field 有默认值,局部变量也是没有默认值的,如果不给它初始值也会报错: ☕️ void run() { int count; count++; // IDE 报错,Variable 'count' might not have been initialized ...
代码语言:javascript 复制 This variable must either have a type annotation or be initialized3. 显式类型声明 ( var 变量名 : 变量类型 (= 变量值) | var age : Byte = 27 | var time_stap : Long | var name : String = “Joe” ) 显示类型声明 : 1.格式 : var 变量名 : 变量类型 (= 变...
intnum =3;//error: variable 'num' is already defined in the scope } System.out.println ("num: "+ num); } 名字遮蔽并不是 Kotlin 发明的,这在编程语言中很常见。在 Java 中我们习惯用方法参数来映射类字段: publicclassShadow{ intval;