I have written the following Java program:
Tab1:
package base;
import java.util.Scanner;
public class Main {
/**
* #param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
Scanner obj = new Scanner(System.in);
System.out.println("Enter first number: ");
int num1 = obj.nextInt();
System.out.println("Enter the second number: ");
int num2 = obj.nextInt();
Add obj1 = new Add();
Mul obj2 = new Mul();
obj1.getData(num1, num2);
int add = obj1.addition();
int mul = obj2.multiplication();
System.out.println("The addition of the two numbers is: " +add);
System.out.println("The multiplication of the two numbers is: " +mul);
}
}
Tab2:
package base;
public class Parent {
int num1, num2;
void getData(int x, int y){
num1 = x;
num2 = y;
}
}
Tab3:
package base;
public class Add extends Parent {
int addition(){
int x;
x = num1 + num2;
return x;
}
}
Tab4:
package base;
public class Mul extends Parent {
int multiplication(){
int x;
x = num1*num2;
return x;
}
}
When I run the code it gives me a result like this:
Enter first number:
5
Enter second number:
4
The addition of the two numbers is: 9
The multiplication of the two numbers is: 0
I have got the same type of result with all kind of different inputs.
The result of the multiplication is always 0
I have cross checked my code several times but apparently I cannot find any mistake.
Where am I going wrong?
Any help will be greatly appreciated.
You should pass argument to Mul instance before calling its method
obj2.getData(num1, num2);
int mul = obj2.multiplication();
There is no call to getData() on obj2:
obj2.getData(num1, num2);
Add obj1 = new Add();
Mul obj2 = new Mul();
obj1.getData(num1, num2);
You created two distinct objects, obj1 and obj2 but put non-zero values only into obj1. The values in obj2 are still zero.
Related
I am trying to learn Java; here is the exercise I am struggling with:
Fermat’s Last Theorem says that there are no integers a, b, and c such that a^n + b^n = c^n except in the case when n = 2.
Write a method named checkFermat that takes four integers as parameters— a, b, c and n—and that checks to see if Fermat’s theorem holds. If n is greater than 2 and it turns out to be true that a^n + b^n = c^n, the program should print “Holy smokes, Fermat was wrong!” Otherwise the program should print “No, that doesn’t work.”
You should assume that there is a method named raiseToPow that takes two integers as arguments and that raises the first argument to the power of the second. For example:
int x = raiseToPow(2, 3);
would assign the value 8 to x, because 2^3 = 8.
I have encountered several problems, for example I can't seem to use Math.Pow(a, n) with an int, only with a double. If you are interested, here is what I have so far, feel free to skip it and just write your own version of the program in the answers.
(Please keep in mind I started this book only a few days back.)
package fermat.s_last_theorem;
import java.lang.Math;
import java.util.Scanner;
public class FermatS_Last_Theorem {
public static void main(String[] args) {
Scanner s = new Scanner (System.in);
System.out.println("Inster First Number");
double frst = s.nextDouble();
System.out.println("Insert Second Number");
double scnd = s.nextDouble();
System.out.println("Insert Exponent");
double expo = s.nextDouble();
double v = FLaw(frst,scnd,expo);
double k = FLawRes(v, expo);
System.out.println("The answer is " + v);
System.out.println("Your answer rooted by your exponent is " + k);
Law(v, Pow(k, expo));
}
public static double Pow(double a, double b) {
double res = Math.pow (a, b);
return (res);
}
public static double FLaw(double frst, double scnd, double expo) {
double D1 = Pow(frst, expo);
double D2 = Pow(scnd, expo);
return (D1 + D2);
}
public static double FLawRes(double res, double base) {
double D3 = Pow(res, 1/base);
return D3;
}
public static void Law(double v, double k) {
if (v==k) {
System.out.println("Pythagora works.");
} else {
System.out.println("Pythagora doesnt work");
}
}
}
The main problem is that I am not exactly sure how to answer the question the exercise asks, and the program listed above does not work as it should.
You should assume that there is a method named raiseToPow ...
That means you write your code using such a method, even though you don't have the method. Your code will be reviewed manually, or teacher may supply the method and run your code.
If you want to test your code, you can always implement it yourself. You should just remove the method before turning in the code.
But the intent here is that this is a write-on-paper exercise.
Now, how to implement int raiseToPow(int a, int b)?
Think about what it means. 34 means 3 * 3 * 3 * 3.
So, implement the method to multiply by a by itself b times.
I'll leave that as another exercise for you.
You can break it out like this :
public boolean checkFermat(int a, int b, int c, int n) {
if(n != 2 &&
(checkFermatCondition(a,b,c,n) ||
checkFermatCondition(a,c,b,n) ||
checkFermatCondition(b,c,a,n))) {
System.out.println("Holy smokes, Fermat was wrong!");
} else {
System.out.println("No, that doesn’t work.");
}
}
In this method you are just trying to reduce you check condition with all of the combinations by calling this method with different parameters
private boolean checkFermatCondition(int a, int b, int c, int n) {
return raiseToPow(a,n)+raiseToPow(b,n) == raiseToPow(c,n);
}
Your function raiseToPow()'s functionality can be achieved using Math.pow:
import java.util.Scanner;
class Main {
public static void main(String[] args) {
Scanner s = new Scanner(System.in);
System.out.println( "Fermat's Last Theorem: a^n+b^n != c^n (n!=2)");
int a, b, c, n;
System.out.print("Enter value for a:");
a = s.nextInt();
System.out.print("Enter value for b:");
b = s.nextInt();
System.out.print("Enter value for c:");
c = s.nextInt();
while(true){
System.out.print("Enter value for n:");
n = s.nextInt();
if(n!=2)
break;
System.out.println("n cannot be 2");
}
checkFremat(a,b,c,n);
}
public static void checkFremat(int a, int b, int c, int n){
if ((int)Math.pow(a, n)+(int)Math.pow(b, n)!=(int)Math.pow(c, n))
System.out.println("Fermat was correct!");
else
System.out.println("Holy smokes, Fermat was wrong!");
}
}
Try it here!
I have some experience using Python so I've been trying to learn Java by writing the same programs I write in Python for school in Java.
I have this function where I enter two integers and it returns the sum. If the integers are the same, then it returns double the sum. For example, 5 + 5 = 20.
I have the following code for this function.
public class sumDouble
{
public int sumDouble(int a, int b) {
int sum = a + b;
if (a == b) {
sum = sum * 2;
}
return sum;
}
}
Next, I want to write a script where I ask the user to input two integers and the main class calls this function. I have the following code for this. Where did I go wrong?
import java.util.Scanner;
public class GetSumFromUser
{
public static void main (String[] args){
Scanner in = new Scanner(System.in);
int a;
int b;
int sumDouble;
sumDouble sum = new sumDouble();
System.out.println("Please enter an integer.");
a = in.nextInt();
System.out.println("You entered "+a);
System.out.println("Please enter another integer.");
b = in.nextInt();
System.out.println("You entered "+b);
System.out.println("Your sum is "+sum);
}
}
At the last line, the output reads "Your sum is sumDouble#1777aec".
You never actually invoked the sumDouble() method. Rather than print out sum (which is an Object), you should print like this:
System.out.println("Your sum is "+sum.sumDouble(a,b));
Try this:
public class SumDouble
{
public static int sumDouble(int a, int b) {
int sum = a + b;
if (a == b) {
sum = sum * 2;
}
return sum;
}
}
...
System.out.println("Your sum is "+SumDouble.sumDouble(a, b));
If you do print(sum) then you are printing the object...
do instead
System.out.println("Your sum is "+sum.sumDouble(a,b));
You get an object from sumDouble class, but you never invoke it's sumDouble method:
sumDouble sum = new sumDouble();
change this to:
sumDouble sd = new sumDouble();
int sum = sd.sumDouble(a,b);
/*
* To change this license header, choose License Headers in Project Properties.
* To change this template file, choose Tools | Templates
* and open the template in the editor.
*/
package test;
import java.util.Scanner;
class sumDouble
{
public int sumDouble(int a,int b)
{
int sum=a+b; //add the numbers
if(a==b) //check if both numbers are same
sum=sum*2; //double th value if same
return sum; //return sum
}
}
public class GetSumFromUser
{
public static void main (String[] args){
Scanner in = new Scanner(System.in);
sumDouble s=new sumDouble();
int a;
int b;
int sum;
System.out.println("Please enter an integer.");
a = in.nextInt();
System.out.println("You entered "+a);
System.out.println("Please enter another integer.");
b = in.nextInt();
System.out.println("You entered "+b);
sum= s.sumDouble(a, b) ; //call the sum double function
System.out.println("Your sum is "+sum);
}
}
System.out.println("Your sum is "+sum);
Change this to:
System.out.println("Your sum is "+sum.sumDouble(a,b));
You haven't called the method. "Your sum is "+sum -this will call the toString method of sum which is sumDouble#1777aec.
I am trying to call a method that has a value that comes from a different method but modified. Here is the code:
import java.util.Scanner;
public class Test{
public static void main(String[] args){
Scanner in = new Scanner(System.in);
int num;
System.out.println("Please enter an integer");
num = in.nextInt();
System.out.println(Multiply(num));
System.out.println(Multiply2(x));
}
public static int Multiply(int num){
int x = num*2;
return x;
}
public static int Multiply2(int x){
int val = x*2;
return val;
}
}
I know I have to declare x inside of main but then I have to initialize it but I want the value of x to equal to the one that equals to the Multiply2 method which multiplies the num from the method, Multiply, by 2. x would be equal to num multiplied by 2; How am I able to do this?
Your methods are exactly the same
The name of the variable doesn't matter. Wheter its called x or val, it makes no difference.
With that in mind, if you want x to be the value returned from your Multiply function, just store that in a variable and use it later. For instance,
int someValue = Multiply(num);
System.out.println(someValue);
System.out.println(Multiply2(someValue));
PS: By convention, we don't capitalize methods names. So they should be multiply and multiply2
import java.util.Scanner;
public class Test {
public static void main(String[] args){
Scanner in = new Scanner(System.in);
int num;
System.out.println("Please enter an integer");
num = in.nextInt();
System.out.println(Multiply(num));
System.out.println(Multiply2(Multiply(num)));
}
public static int Multiply(int num) {
int x = num * 2;
return x;
}
public static int Multiply2(int x) {
int val = x * 2;
return val;
}
}
We have an assignment in class to create a greatest common divider (gcd) program using functions. I missed out on the lesson where we learned how to properly use them. I finished the part that actually does the division but I don't know how to separate it into a function and have it work. I'd like to have the input in the main class and the process in function.
This is what I have, it does not work when I run it
package gcd.function.java.program;
import java.util.Scanner;
/**
*
* #author sarah_000
*/
public class GCDFunctionJavaProgram {
public static void main(String[] args) {
int num1;
int num2;
int div;
Scanner input = new Scanner(System.in);
System.out.print("Enter your first number: ");
num1 = input.nextInt();
System.out.print("Enter your second number: ");
num2 = input.nextInt();
System.out.printf("The GCD is %d ", div);
}
public static void GCDFunction() {
if(num1 > num2)
div = num2;
else div = num1;
while((num1 % div!= 0)||(num2 % div != 0))
{
div --;
}//end of while loop
}
}
Any tips or help you can give to me will be greatly appreciated, I'm very new
You declare two parameters and modify the return type in your GCDFunction like this:
public static int GCDFunction(int num1, int num2)
You are currently trying to access the variables in the main method but are out of scope.
Also, you never actually call your GCDFunction
Think of it like passing functions in math. The GCDFunction() has to receive the numbers into the function so we do
public static void GCDFunction(int num1, int num2)
That also lets Java know the type it is, type int. And your java variables are scoped inside of the functions so you have to print the output in the function that created the variable in your scenario.
So once you have that function set up to receive the variables and output after processing, you call the function in the main with a
GCDFunction(num1, num2);
Where num1 and num2 are the variables that have your integers stored in.
The end result after a little rearranging looks like this.
import java.util.Scanner;
public class GCDFunctionJavaProgram {
public static void main(String[] args) {
int num1;
int num2;
Scanner input = new Scanner(System.in);
System.out.print("Enter your first number: ");
num1 = input.nextInt();
System.out.print("Enter your second number: ");
num2 = input.nextInt();
GCDFunction(num1, num2);
}
public static void GCDFunction(int num1, int num2) {
int div;
if(num1 > num2){
div = num2;
}
else{ div = num1;}
while((num1 % div!= 0)||(num2 % div != 0))
{
div --;
}//end of while loop
System.out.printf("The GCD is %d ", div);
}
Trying to give you a example of how the code should be to take in variable number of parameters.
public int gcd(Integer... numbers) {
int gcd = 1;
int miNNumber=Collections.min(Arrays.asList(numbers));
boolean isDivisible;
for(int i=2; i<=miNNumber;i++) {
isDivisible=true;
for(Integer eachNumber : numbers) {
if(eachNumber%i!=0) {
isDivisible=false;
break;
}
}
if(isDivisible) {
gcd=i;
}
}
return gcd;
}
You can call it
gcd(10, 200, 400);
or
gcd(10, 200, 400, 4000, 40);
import java.io.IOException;
import java.util.*;
public class calling {
public static String s;
public static String t;
public static int y;
public static int x;
public static int num1() {
int x;
Scanner scanner = new Scanner (System.in);
System.out.println("Please enter a number called x: ");
x=scanner.nextInt();
return x;
}
public static int num2() {
int y;
Scanner scanner = new Scanner (System.in);
System.out.println("Please enter a second number called y: ");
y=scanner.nextInt();
return y;
}
public static void calculation() {
Scanner input = new Scanner(System.in);
System.out.println("What process would you like to do? *, /, + or - ?");
s=input.next();
if (s.equals("*")) {
System.out.println("\nThe product of these numbers is:" + (x*y));}
else
if (s.equals("+")) {
System.out.println("\nThe sum of these numbers is: " + (x+y));}
System.out.println("\nDo you want x or y to be the dividor/subtractor?: ");
t=input.next();
if (t.equals("y") || t.equals("Y") ) {
if (s.equals("/")) {
System.out.println("\nThe quotient of these numbers is: " + (x/y));}
else
if (s.equals("-")) {
System.out.println("\nThe difference of these numbers is: " + (x-y));}}
else
if (t.equals("x") || t.equals("X")){
if (s.equals("/")) {
System.out.println("\nThe quotient of these numbers is: " + (y/x));}
else
if (s.equals("-")) {
System.out.println("\nThe difference of these numbers is: " + ((y-x)));}}
}
public static void main (String [] args) throws IOException {
num1();
num2();
calculation();
}
}
i keep getting this error in what should be my final result which is simply the result of the calculations being performed
this is the error:" Exception in thread "main" java.lang.ArithmeticException: / by zero
at calling.calculation(calling.java:44)
at calling.main(calling.java:64)"
Since this is likely homework, I'll give you a hint to point you in the right direction.
When you run your program, you execute num1 and num2 to collect the values of x and y from the user. Within num2, y is declared as a local variable. What happens to that variable when num2 returns? And what does that imply for the class field (variable) y declared on line 7?
This is also a good time to learn how to use a debugger. Put a breakpoint on line 44, and see what the values of x and y are.
You need to make sure that the:
int x;
int y;
are the ones you want. Integer's default to zero when static.