scala重载无参构造方法

Scala无参数方法 (Scala parameterless method)

A method which accepts no parameters from the calling code. It also denotes that there will not be any empty parentheses. These are special types of methods in Scala that are initialized and called especially. To initialize parameterless method you need to use the name with def keyword but w/o the "( )" parenthesis. While calling the method also we will avoid using the "( )" parenthesis.

一种不从调用代码接受任何参数的方法。 它还表示不会有任何空括号。 这些是Scala中特殊的方法类型，这些方法特别进行了初始化和调用。 要初始化无参数方法，您需要使用带def关键字的名称，但不带“()”括号。 在调用该方法时，我们也将避免使用“()”括号。

Syntax:

句法：

    def method_name = code_to_be_executed

Program to illustrate parameterless method

说明无参数方法的程序

class calculator(a: Int, b: Int)
{
def add = println("a+b = " + (a+b))
def subtract = println("a-b = " + (a-b))
def product = println("a*b = "+ (a*b) )
def division = println("a/b = " + (a/b))
}
object Main
{
def main(args: Array[String])
{
val calc = new calculator(1250, 50)
println("value of a = 1250 and b =  50")
calc.add
calc.subtract
calc.product
calc.division
}
}

Output

输出量

value of a = 1250 and b =  50
a+b = 1300
a-b = 1200
a*b = 62500
a/b = 25

Explanation:

说明：

This code initializes a class calculator and defines 4 parameterless methods in it. These methods are used to add, subtract, multiply and divide values. These methods directly print the calculated values and do not accept any parameters. The object calc of the class calculator is created with values 1250 and 50. Then with this calc object, we will call all the four methods that perform operations and returns output.

此代码初始化一个类计算器，并在其中定义4个无参数的方法 。 这些方法用于加，减，乘和除值。 这些方法直接打印计算值，不接受任何参数。 将使用值1250和50创建类计算器的对象calc 。 然后，使用该calc对象，我们将调用执行操作并返回输出的所有四个方法。

The parameterless method is invoked without the () parenthesis. And there is an error if we call a parameterless method using the parenthesis.

无参方法在不带()括号的情况下调用。 如果我们使用括号调用无参数方法 ，则会出现错误。

If the programmer by mistake puts a parenthesis at the end of the function call, the compiler would report an error stating: "Unit does not take parameters".

如果程序员错误地在函数调用的末尾加上了括号，则编译器将报告错误，指出：“单元不带参数”。

Program to show error when parameterless method is called using parentheses

程序在使用括号调用无参数方法时显示错误

class calculator(a: Int, b: Int)
{
def division = println("a/b = " + (a/b))
}
object Main
{
def main(args: Array[String])
{
val calc = new calculator(1250, 50)
println("value of a = 1250 and b =  50")
calc.division()
}
}

Output

输出量

/home/jdoodle.scala:12: error: Unit does not take parameterscalc.division()^
one error found

Explanation:

说明：

This code has the same logic as the former code. The difference is just that while calling the division parameterless method parenthesis is used. Due to this, the compiler gives an error: "Unit does not take parameters".

此代码与以前的代码具有相同的逻辑。 区别只是在调用除法无参数方法时使用了括号。 因此，编译器将给出错误：“单元不带参数”。

Bonus : parameterless method Vs method without parameter

奖励：无参数方法与无参数方法

Scala has supports multiple types of parameter passing in its methods.

Scala在其方法中支持多种类型的参数传递。

But these two methods look quite similar but have different functionalities. The parameterless method does not accept and sort of parameter in its call. But the method without parameter accepts void parameter in its call ( nothing can be treated as a parameter).

但是这两种方法看起来很相似，但是功能不同。 无参数方法在其调用中不接受参数并对其进行排序。 但是不带参数的方法在其调用中接受void参数(不能将任何内容视为参数)。

翻译自: https://www.includehelp.com/scala/parameterless-method-in-scala.aspx

scala重载无参构造方法