Java中的基本计算器

Question

我正在尝试用Java创建一个基本的calculator 。 我对编程很陌生，所以我试着习惯它。

import java.util.Scanner;
import javax.swing.JOptionPane;

public class javaCalculator 
{

    public static void main(String[] args) 
    {
        int num1;
        int num2;
        String operation;


        Scanner input = new Scanner(System.in);

        System.out.println("please enter the first number");
        num1 = input.nextInt();

        System.out.println("please enter the second number");
        num2 = input.nextInt();

        Scanner op = new Scanner(System.in);

        System.out.println("Please enter operation");
        operation = op.next();

        if (operation == "+");
        {
            System.out.println("your answer is" + (num1 + num2));
        }
        if  (operation == "-");
        {
            System.out.println("your answer is" + (num1 - num2));
        }

        if (operation == "/");
        {
            System.out.println("your answer is" + (num1 / num2));
        }
        if (operation == "*")
        {
            System.out.println("your answer is" + (num1 * num2));
        }


    }
}

这是我的代码。 它提示输入数字和操作，但是一起显示答案？

Answer 1

从if语句中删除分号，否则后面的代码将是独立的 ，并将始终执行：

if (operation == "+");
                     ^

也可以使用.equals for Strings ， ==比较Object引用：

 if (operation.equals("+")) {

Answer 2

Here is simple code for calculator so you can consider this
import java.util.*;
import java.util.Scanner;
public class Hello {
    public static void main(String[] args)
    {
        System.out.println("Enter first and second number:");
        Scanner inp= new Scanner(System.in);
        int num1,num2;
        num1 = inp.nextInt();
        num2 = inp.nextInt();
        int ans;
        System.out.println("Enter your selection: 1 for Addition, 2 for substraction 3 for Multiplication and 4 for division:");
        int choose;
        choose = inp.nextInt();
        switch (choose){
        case 1:
            System.out.println(add( num1,num2));
            break;
        case 2:
            System.out.println(sub( num1,num2));
            break;      
        case 3:
            System.out.println(mult( num1,num2));
            break;
        case 4:
            System.out.println(div( num1,num2));
            break;
            default:
                System.out.println("Illigal Operation");


        }



    }
    public static int add(int x, int y)
    {
        int result = x + y;
        return result;
    }
    public static int sub(int x, int y)
    {
        int result = x-y;
        return result;
    }
    public static int mult(int x, int y)
    {
        int result = x*y;
        return result;
    }
    public static int div(int x, int y)
    {
        int result = x/y;
        return result;
    }

}

Answer 3

CompareStrings与equals(..)不与==

if (operation.equals("+")
{
    System.out.println("your answer is" + (num1 + num2));
}
if (operation.equals("-"))
{
    System.out.println("your answer is" + (num1 - num2));
}
if (operation.equals("/"))
{
    System.out.println("your answer is" + (num1 / num2));
}
if (operation .equals( "*"))
{
    System.out.println("your answer is" + (num1 * num2));
}

并且; 条件是一个空的陈述之后所以条件根本没有效果。

如果使用java 7，还可以用switch替换if语句。
在java <7中，您可以测试，如果operation长度为1，则为char [ switch (operation.charAt(0)) ]进行switch (operation.charAt(0))

Answer 4

用于制作简单计算器的Java程序示例：

import java.util.Scanner;

public class Calculator
{
public static void main(String args[])
{
    float a, b, res;
    char select, ch;
    Scanner scan = new Scanner(System.in);

    do
    {
        System.out.print("(1) Addition\n");
        System.out.print("(2) Subtraction\n");
        System.out.print("(3) Multiplication\n");
        System.out.print("(4) Division\n");
        System.out.print("(5) Exit\n\n");
        System.out.print("Enter Your Choice : ");
        choice = scan.next().charAt(0);

        switch(select)
        {
            case '1' : System.out.print("Enter Two Number : ");
                a = scan.nextFloat();
                b = scan.nextFloat();
                res = a + b;
                System.out.print("Result = " + res);
                break;
            case '2' : System.out.print("Enter Two Number : ");
                a = scan.nextFloat();
                b = scan.nextFloat();
                res = a - b;
                System.out.print("Result = " + res);
                break;
            case '3' : System.out.print("Enter Two Number : ");
                a = scan.nextFloat();
                b = scan.nextFloat();
                res = a * b;
                System.out.print("Result = " + res);
                break;
            case '4' : System.out.print("Enter Two Number : ");
                a = scan.nextFloat();
                b = scan.nextFloat();
                res = a / b;
                System.out.print("Result = " + res);
                break;
            case '5' : System.exit(0);
                break;
            default : System.out.print("Wrong Choice!!!");
        }
    }while(choice != 5);       
}
}

Answer 5

import java.util.Scanner;
public class AdditionGame {

public static void main(String[] args) {
    // TODO Auto-generated method stub

    int num1;
    int num2;
    String operation;

    Scanner input = new Scanner(System.in);

    System.out.println("Please Enter The First Number");
    num1 = input.nextInt();

    System.out.println("Please Enter The Second Number");
    num2 = input.nextInt();

    Scanner op = new Scanner (System.in);

    System.out.println("Please Enter The Operation");
    operation = op.next();

    if (operation.equals("+"))
    {
        System.out.println("Your Answer is "+(num1 + num2));
    }
    else if (operation.equals("-"))
    {
        System.out.println("Your Answer is "+(num1 - num2));
    }       
    else if (operation.equals("*"))
    {
        System.out.println("Your Answer is "+(num1 * num2));
    }   
    else if (operation.equals("/"))
    {
        System.out.println("Your Answer is "+(num1 / num2));
    }
}

}

Answer 6

也许它更好地使用case而不是if dunno如果这消除了错误，但它更清洁我认为.. switch (operation){case +: System.out.println("your answer is" + (num1 + num2));break;case -: System.out.println("your answer is" - (num1 - num2));break; ... switch (operation){case +: System.out.println("your answer is" + (num1 + num2));break;case -: System.out.println("your answer is" - (num1 - num2));break; ...

Answer 7

import java.util.Scanner; import javax.swing.JOptionPane;

public class javaCalculator {

public static void main(String[] args) 
{
    int num1;
    int num2;
    String operation;


    Scanner input = new Scanner(System.in);

    System.out.println("please enter the first number");
    num1 = input.nextInt();

    System.out.println("please enter the second number");
    num2 = input.nextInt();

    Scanner op = new Scanner(System.in);

    System.out.println("Please enter operation");
    operation = op.next();

    if (operation.equals("+"))
    {
        System.out.println("your answer is" + (num1 + num2));
    }
   else if  (operation.equals("-"))
    {
        System.out.println("your answer is" + (num1 - num2));
    }

  else if (operation.equals("/"))
    {
        System.out.println("your answer is" + (num1 / num2));
    }
   else if (operation.equals("*"))
    {
        System.out.println("your answer is" + (num1 * num2));
    }
   else 
    {
       System.out.println("Wrong selection");
    }


}

}

Answer 8

public class SwitchExample {

    public static void main(String[] args) throws Exception {
        System.out.println(":::::::::::::::::::::Start:::::::::::::::::::");
        System.out.println("\n\n");

        System.out.println("1. Addition");
        System.out.println("2. Multiplication");
        System.out.println("3. Substraction");
        System.out.println("4. Division");
        System.out.println("0. Exit");
        System.out.println("\n");

        System.out.println("Enter Your Choice :::::::  ");
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        String str = br.readLine();

        int usrChoice = Integer.parseInt(str);

        switch (usrChoice) {
            case 1:
                doAddition();
                break;
            case 2:
                doMultiplication();
                break;
            case 3:
                doSubstraction();
                break;
            case 4:
                doDivision();
                break;

            case 0:
                System.out.println("Thank you.....");
                break;

            default:
                System.out.println("Invalid Value");
        }

        System.out.println(":::::::::::::::::::::End:::::::::::::::::::");
}

public static void doAddition() throws Exception {
    System.out.println("******* Enter in Addition Process ********");

    String strNo1, strNo2;

    System.out.println("Enter Number 1 For Addition : ");
    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    strNo1 = br.readLine();

    System.out.println("Enter Number 2 For Addition : ");
    BufferedReader br1 = new BufferedReader(new InputStreamReader(System.in));
    strNo2 = br1.readLine();

    int no1 = Integer.parseInt(strNo1);
    int no2 = Integer.parseInt(strNo2);

    int result = no1 + no2;

    System.out.println("Addition of " + no1 + " and " + no2 + " is ::::::: " + result);
}

public static void doSubstraction() throws Exception {
    System.out.println("******* Enter in Substraction Process ********");

    String strNo1, strNo2;

    System.out.println("Enter Number 1 For Substraction : ");
    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    strNo1 = br.readLine();

    System.out.println("Enter Number 2 For Substraction : ");
    BufferedReader br1 = new BufferedReader(new InputStreamReader(System.in));
    strNo2 = br1.readLine();

    int no1 = Integer.parseInt(strNo1);
    int no2 = Integer.parseInt(strNo2);

    int result = no1 - no2;

    System.out.println("Substraction of " + no1 + " and " + no2 + " is ::::::: " + result);
}

public static void doMultiplication() throws Exception {
    System.out.println("******* Enter in Multiplication Process ********");

    String strNo1, strNo2;

    System.out.println("Enter Number 1 For Multiplication : ");
    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    strNo1 = br.readLine();

    System.out.println("Enter Number 2 For Multiplication : ");
    BufferedReader br1 = new BufferedReader(new InputStreamReader(System.in));
    strNo2 = br1.readLine();

    int no1 = Integer.parseInt(strNo1);
    int no2 = Integer.parseInt(strNo2);

    int result = no1 * no2;

    System.out.println("Multiplication of " + no1 + " and " + no2 + " is ::::::: " + result);
}

public static void doDivision() throws Exception {
    System.out.println("******* Enter in Dividion Process ********");

    String strNo1, strNo2;

    System.out.println("Enter Number 1 For Dividion : ");
    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    strNo1 = br.readLine();

    System.out.println("Enter Number 2 For Dividion : ");
    BufferedReader br1 = new BufferedReader(new InputStreamReader(System.in));
    strNo2 = br1.readLine();

    int no1 = Integer.parseInt(strNo1);
    int no2 = Integer.parseInt(strNo2);

    float result = no1 / no2;

    System.out.println("Division of " + no1 + " and " + no2 + " is ::::::: " + result);
}

}

Answer 9

我们可以简单地使用in.next（）。charAt（0）; 通过初始化操作作为一个char * /操作的角色-分配+。

import java.util。*; 公共类计算器{

public static void main(String[] args) {

Scanner in = new Scanner(System.in);

char operation;
int num1;
int num2;

 System.out.println("Enter First Number");

num1 = in.nextInt();

System.out.println("Enter Operation");

operation = in.next().charAt(0);

System.out.println("Enter Second Number");

num2 = in.nextInt();

if (operation == '+')//make sure single quotes
{
    System.out.println("your answer is " + (num1 + num2));
}
if (operation == '-')
{
    System.out.println("your answer is " + (num1 - num2));
}
if (operation == '/')
{
    System.out.println("your answer is " + (num1 / num2));
}
if (operation == '*')
{
    System.out.println("your answer is " + (num1 * num2));
}

}

}

Answer 10

import java.util.Scanner;
public class JavaApplication1 {


    public static void main(String[] args) {

         int x,
         int y;

         Scanner input=new Scanner(System.in);
         System.out.println("Enter Number 1");
         x=input.nextInt();
         System.out.println("Enter Number 2");
         y=input.nextInt();

         System.out.println("Please enter operation + - / or *");
         Scanner op=new Scanner(System.in);
         String operation = op.next();

         if (operation.equals("+")){
             System.out.println("Your Answer: " + (x+y));
         }
         if (operation.equals("-")){
             System.out.println("Your Answer: "+ (x-y));
         }
         if (operation.equals("/")){
             System.out.println("Your Answer: "+ (x/y));
         }
         if (operation.equals("*")){
            System.out.println("Your Answer: "+ (x*y));
         }
    }

}