Calculator program in Java is used by programmer to add, subtract, multiply or divide two integer numbers that are input by system. In the given example a class "calculator" is used.
System.in takes the input from the system/user at run time. InputStreamReader reads the input from System.in and then keep it into Buffer.
parseInt method of Integer class is used to convert the strings into integers. If the user enters a "+" operator it will add the two integer numbers and display the result. If the user enters a "" operator it will subtract the two numbers (if the first entered number is bigger then the second entered number the result will be a positive value otherwise it will be a negative value).
If the user enters a "*" operator it will multiply the two numbers. And if the users enters a "/" it will divide the two numbers (if the first entered number is bigger then the second entered number the result will be a integer value other wise it will be a fraction value)
Example of Calculator program in Java
package Tutorial; import java.io.*; class calculator { public static void main(String[] args) throws IOException { BufferedReader reader = new BufferedReader(new InputStreamReader( System.in)); double x, y, store = 0; char cal; System.out.println("Enter the two numbers: "); x = Integer.parseInt(reader.readLine()); y = Integer.parseInt(reader.readLine()); System.out.println("Enter the operator: "); cal = (char) System.in.read(); if (cal == '+') { store = x + y; } else if (cal == '') { if (x > y) store = x  y; if(x < y) store= x  y; } else if (cal == '*') { store = x * y; } else if (cal == '/') { if (x > y) store = x / y; if( x < y) store = x / y; } else System.out.println("Wrong operator: "); System.out.println("The result is: " + store); } }
Output:
Enter the two numbers:
12
10
Enter the operator:
*
The result is: 120
Enter the two numbers:
12
14
Enter the operator:

The result is: 2.0
Enter the two numbers:
12
6
Enter the operator:
/
The result is: 2.0
Enter the two numbers:
20
20
Enter the operator:
+
The result is: 40.0
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