[英]Methods in subclass aren't working
我的任务是创建一个添加到现有超类上的子类,该类由带有主方法的第三类运行,该主方法创建子类的对象并调用适当的方法。
我的问题是,在超类中调用方法可以正常工作,但是调用我在子类中编写的两个其他方法会被忽略。
我已经检查过了,主要方法是进入if语句,该语句在子类中调用new方法,但是此方法未执行。
特别地,超类是具有基本加,减,除和乘选项以及清除当前值的选项的内存计算器。 子类是一个科学的内存计算器,它会覆盖超类中的菜单方法,以包含幂和对数的选项,并同时具有这两种方法。
当我选择电源选项时,它只是返回当前值,而不是将该电源提高到指定的数字。
超类:
import java.util.Scanner;
public class MemoryCalc {
private double currentValue = 0;
public static int displayMenu() {
Scanner input = new Scanner(System.in);
System.out.print("Menu\n1. Add\n2. Subtract\n3. Multiply\n4. Divide\n5. Clear\n6. Quit\nWhat would you like to do? ");
int menuChoice = input.nextInt();
while (menuChoice < 1 || menuChoice > 6) {
System.out.print("Please enter a valid option.\n\n");
System.out.print("Menu\n1. Add\n2. Subtract\n3. Multiply\n4. Divide\n5. Clear\n6. Quit\nWhat would you like to do? ");
menuChoice = input.nextInt();
}
return menuChoice;
}
public static double getOperand(String prompt) {
Scanner input = new Scanner(System.in);
System.out.print(prompt);
double operand = input.nextDouble();
return operand;
}
public double getCurrentValue() {
return currentValue;
}
public void add(double operand2) {
currentValue = currentValue + operand2;
}
public void subtract(double operand2) {
currentValue = currentValue - operand2;
}
public void multiply(double operand2) {
currentValue = currentValue * operand2;
}
public void divide(double operand2) {
if (operand2 == 0) {
currentValue = Double.NaN;
}
else currentValue = currentValue / operand2;
}
public void clear() {
currentValue = 0;
}
}
子类:
import java.util.Scanner;
public final class ScientificMemCalc extends MemoryCalc {
private double currentValue = 0;
public static int displayMenu() {
Scanner input = new Scanner(System.in);
int menuChoice = -1;
while (menuChoice < 1 || menuChoice > 8) {
System.out.println();
System.out.println("Menu");
System.out.println("1. Add");
System.out.println("2. Subtract");
System.out.println("3. Multiply");
System.out.println("4. Divide");
System.out.println("5. Power");
System.out.println("6. Logarithm");
System.out.println("7. Clear");
System.out.println("8. Quit");
System.out.println();
System.out.print("What would you like to do? ");
menuChoice = input.nextInt();
if (menuChoice < 1 || menuChoice > 8) {
System.out.println(menuChoice + " wasn't one of the options");
}
}
return menuChoice;
}
public void power(double operand2) {
currentValue = Math.pow(currentValue, operand2);
}
public void logarithm() {
currentValue = Math.log(currentValue);
}
}
主要方法:
public class ScientificCalcDriver {
public static void main(String[] args) {
ScientificMemCalc calculator1 = new ScientificMemCalc();
int menuChoice = 0;
while (menuChoice != 8) {
System.out.print("The current value is " + calculator1.getCurrentValue() + "\n");
menuChoice = ScientificMemCalc.displayMenu();
if (menuChoice < 6) {
double Operand2 = ScientificMemCalc.getOperand("What is the second number? ");
if (menuChoice == 1) {
calculator1.add(Operand2);
}
if (menuChoice == 2) {
calculator1.subtract(Operand2);
}
if (menuChoice == 3) {
calculator1.multiply(Operand2);
}
if (menuChoice == 4) {
calculator1.divide(Operand2);
}
if (menuChoice == 5) {
calculator1.power(Operand2);
}
}
else if (menuChoice == 6) {
calculator1.logarithm();
}
else if (menuChoice == 7) {
calculator1.clear();
}
else if (menuChoice == 8) {
System.out.print("Goodbye!");
System.exit(0);
}
}
}
}
您有两个不同的currentValue
变量,它们都是私有的,一个在超类中,一个在子类中。 您超类中的方法正在更改其变量的值,而子类中的方法正在更改其变量的值。
使currentValue
在超类中受保护,并将其从子类中删除。
基于“必须是私有的”注释:您仍然需要删除子类中多余的currentValue
变量,但是正如Oleg指出的那样,您可以使用在以下代码中定义的get和set方法获取并更新超类中私有变量的值。超类。
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