Unspecified value parameters name, age. val s = new Student ^ scala> val s = new Student("jom",23) your name is jom,your age is 23 s: Student = Student@2d70f312 //给默认值 scala> :paste // Entering paste mode (ctrl-D to finish) class Student(val name:String="leo",val age:...
Traits cannot have constructor parameters. Abstract class code is fully interoperable and can be instantiated directly. Trait code is interoperable until implemented and cannot be instantiated directly. Abstract classes cannot be added to object instances; they must be extended. Traits can be mixed into...
类MyClass中定义了一个私有成员变量secret和一个方法printCompanionSecret,用于打印伴生对象中的私有成员变量companionSecret。而伴生对象MyClass中定义了一个私有成员变量companionSecret和一个方法printSecret,用于打印类MyClass的实例中的私有成员变量secret。 在主程序中,创建了一个类MyClass的实例a,并调用了它的printComp...
传名参数(Call-by-Name Parameters)是一种特殊的参数传递方式,它允许我们将表达式作为参数传递给函数,并在需要时进行求值。传名参数使用=>符号来定义,以表示传递的是一个表达式而不是具体的值。 传名参数的特点是,在每次使用参数时都会重新求值表达式,而不是在调用函数时进行求值。这样可以延迟表达式的求值,只在需要...
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Here, return type could be any valid Scala data type and list of parameters will be a list of variables separated by comma and list of parameters and return type are optional. Very similar to Java, a return statement can be used along with an expression in case function returns a value....
Only the order and the type of the parameters is used to match.The following example transforms each row to the correct Scala type:case class SmallCountry(name:String) case class BigCountry(name:String) case class France val countries = SQL("SELECT name,population FROM Country WHERE id = {...
Scala语言来源于Java,它以Java虚拟机(JVM)为运行环境,Scala源码 (.scala)会编译成.class文件。这意味着Scala程序可以与Java程序互操作,并且可以利用JVM的优化和性能。 在语法上,Scala和Java有一些区别。 例如,在Scala中,一切皆为对象,而在Java中,基本类型、null、静态方法等不是对象。在Scala中,成员变量/属性必须...
classCounter{privatevarvalue=0// 必须初始化字段defincrement(){ value +=1}// 方法默认公有defcurrent=value//无参方法}valmyCounter=newCountermyCounter.current()// 调用必须是myCounter.current这种风格<console>:10: error: Int does not take parameters ...
A Trait can only have parameter-less constructor, while an Abstract can have multiple constructors with parameters); (trait是没有构造函数的,如果说有的话就是不带参数的。抽象类可以有多个构造函数) An Abstract class is fully interoperable(完全可互操作) with Java, while a Trait is interoperable onl...