你好我是java新手，需要有人来回答我遇到的问题。我最近开始了一个用Java制作计算器的项目。然而，我的代码有一个问题。基本上，我不能从方法中调用字符串。我试过各种各样的方法来解决这个问题，但都无济于事这是代码：
package CalculatorCore;
import java.util.Scanner;
public class calculations {
static void firstNumber() {
Scanner firstNum = new Scanner(System.in);
System.out.print("First Number: ");
String n1 = firstNum.next(); //You can see, i put the string in a method
}
static void secondNumber() {
Scanner secondNum = new Scanner(System.in);
System.out.print("Second Number: ");
String n2 = secondNum.next(); //Here too
}
public static void main(String[] args) {
System.out.println("Please Choose one of the following equasions: +, -, * or /");
System.out.println("");
System.out.println("");
mathEquasions();
}
static void mathEquasions() {
Scanner equasions = new Scanner(System.in);
System.out.print("Enter input: ");
String e = equasions.next();
if (e.equals("+")) {
System.out.println("");
System.out.println("Please enter the first number that you want to add");
firstNumber();
System.out.println("");
System.out.println("Now add the second number");
secondNumber();
var plusAnswer = (n1 + n2); /*The problem is situated here, i need to call the
strings from another class*/
System.out.println("");
System.out.println("");
System.out.println("Your answer is...");
firstNumber();.n1
}
}
我已经使用了使用户输入紧凑的方法，所以如果没有其他方法，我应该删除这些方法吗？
您需要返回在两个方法中检索到的数字。不要忘记使用nextInt:将它们解析为整数
public class calculations {
static int firstNumber() {
Scanner firstNum = new Scanner(System.in);
System.out.print("First Number: ");
int n1 = firstNum.nextInt();
return n1;
}
static int secondNumber() {
Scanner secondNum = new Scanner(System.in);
System.out.print("Second Number: ");
int n2 = secondNum.nextInt();
return n2;
}
}
然后，当调用firstNumber或secondNumber时，创建新的变量来存储它们的返回值：
public class calculations {
static void mathEquasions() {
Scanner equasions = new Scanner(System.in);
System.out.print("Enter input: ");
String e = equasions.next();
if (e.equals("+")) {
System.out.println("");
System.out.println("Please enter the first number that you want to add");
int n1 = firstNumber();
System.out.println("");
System.out.println("Now add the second number");
int n2 = secondNumber();
var plusAnswer = (n1 + n2);
System.out.println("");
System.out.println("");
System.out.println("Your answer is...");
}
}
}
欢迎加入SO！当你第一次尝试某件事时，最好尽可能简单，然后逐渐使用更复杂的技术。
在这种情况下，所有的东西都已经在一个类中了，所以作为第一步，您可以尝试将所有代码放回main method中。
public static void main(String[] args) {
//All your code can come here first in the order they are supposed to to be called.
}
作为第二步，当一切正常时，您可以将重复代码的部分提取到单独的方法中。就像这里一样，你可以只拥有一个firstNumber()和secondNumber()，比如：
static int getNumber() {
Scanner scanner = new Scanner(System.in);
System.out.print("Number: ");
int number = scanner.nextInt();
return number;
}
你可以调用相同的方法来获得两个号码：
public static void main(String[] args) {
//...
System.out.println("Please enter the first number that you want to add");
int n1 = getNumber(); // Using the same method for both
System.out.println("");
System.out.println("Now add the second number");
int n2 = getNumber(); // Using the same method for both
//...
}
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