Question

所以......这是我在Stack上的第一篇文章，我也是Java的新手（完全是编程）。我试图创建一个简单的命令行应用程序，用于计算员工和＃39;利润取决于产生的收入。已经做到了但是我现在正在学习功能界面和lambdas，我想尝试使用它们。在下面你可以找到代码。

package BalanceCounter;

import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;

public class Main {
public static void main(String[] args) {

    Scanner input = new Scanner(System.in);
    System.out.print("Number of employees: ");
    int empCounter = input.nextInt();
    System.out.println();

    List<Employee> employees = new ArrayList<>(empCounter);
    for (int i = 0; i < empCounter; i++) {
        employees.add(new Employee());
    }

    for (Employee employee : employees) {
        System.out.println("Employee: " + employee.getEmpName()
                + "\nBase salary: " + employee.getEmpBaseSalary()
                + "\nProfit from income: " + employee.getEmpBonus()
                + "\n");
    }
}
}

这里是注释块中带有getEmpBonus（）方法的Employee类。那是我尝试使用功能界面的地方。

package BalanceCounter;

import java.util.Scanner;

class Employee {
private String empName;
private double empBaseSalary;
private double empIncome;
private double empBonus;


Employee() {
    Scanner input = new Scanner(System.in);

    System.out.print("Employees name: ");
    setEmpName(input.nextLine());

    System.out.print("Type basic salary: ");
    setEmpSalary(input.nextDouble());

    System.out.print("Generated income: ");
    setEmpIncome(input.nextDouble());
    setEmpBonus();

    System.out.println();
}

/*
 * Here are all the setters
 */

private void setEmpName(String empName) {
    this.empName = empName;
}

private void setEmpSalary(double empBaseSalary) {
    this.empBaseSalary = empBaseSalary;
}

private void setEmpIncome(double empIncome) {
    this.empIncome = empIncome;
}

private void setEmpBonus() {
    if (getEmpIncome() <= 10000)
        empBonus = (getEmpIncome() * 3) / 100;
    else if (getEmpIncome() > 10000 && getEmpIncome() <= 20000)
        empBonus = (getEmpIncome() * 2) / 100;
    else empBonus = (getEmpIncome() * 1) / 100;
}


/*
 * Time for the getters
 */

String getEmpName() {
    return empName;
}

double getEmpBaseSalary() {
    return empBaseSalary;
}

private double getEmpIncome() {
    return empIncome;
}

double getEmpBonus() {
    return empBonus;
}

/*
 * double getEmpBonus(Calculation calculation) {
 * return empBonus = calculation.calculate(this.empBonus);
 * }
 */

}

最后一件事是计算界面。

package BalanceCounter;


public interface Calculation {
    double calculate(double arg);
}

class CalcBonus implements Calculation{
    public double calculate(double empBonus) {
        return empBonus;
    }
}

很抱歉很长的帖子但是想给你我所有的信息。如果你在我的代码中看到一些错误和坏习惯 - 请告诉我。亲切的问候。

Answer 1

此界面：

public interface Calculation {
    double calculate(double arg);
}

与DoubleUnaryOperator：

具有相同的合同

@FunctionalInterface
public interface DoubleUnaryOperator {
    double applyAsDouble(double operand);
   ...
}

所以你真的不需要为此引入一个新界面你可以使用内置的但是如果你想真正强调方法的名称和/或参数。

作为一般方法，请在创建之前查看内置功能接口是否与您的要求不匹配。

假设您现在取消注释方法，并且想要使用此方法：

  double getEmpBonus(DoubleUnaryOperator calculation) {
     return empBonus = calculation.applyAsDouble(this.empBonus);
  }

如果你想传递一个加倍奖金的实现，你必须创建一个子类或匿名类：

class DoubleBonus implements DoubleUnaryOperator {
    public double applyAsDouble(double operand) {
        return operand * 2;
    }
}

lambda的想法是你可以使用lambda表达式内联子类你可以这样调用方法：

double doubledBonus = getEmpBonus(empBonus->empBonus*2);

您不再需要子类或匿名类。

Answer 2

package training;
public class Calculator {
    interface IntegerMath {
        int operation(int a, int b);
    }
    interface RealMath {
        double operation(double a, double b);
    }
    public int operateBinary(int a, int b, IntegerMath op) {
        return op.operation(a, b);
    }
    public double operateBinary(int a, int b, RealMath op) {
        return op.operation(a, b);
    }
    public static void main(String... args) {
        Calculator cal = new Calculator();
        IntegerMath addition = (a, b) -> a + b;
        IntegerMath subtraction = (a, b) -> a - b;
        IntegerMath multiplication = (a, b) -> a * b;
        RealMath division = (a, b) -> a / b;
                System.out.println("Add: 40 + 22 = " +
                cal.operateBinary(40, 22, addition));
        System.out.println("Sub: 120 - 80 = " +
                cal.operateBinary(120, 80, subtraction));
        System.out.println("Mul: 12 * 12 = " +
                cal.operateBinary(12, 12, multiplication));
        System.out.println("Div: 478 / 12 = " +
                cal.operateBinary(478, 12, division));
    }
}

JAVA - 使用功能界面进行计算

2 个答案: