Managing multiple instances of same class (Java)

Question

Hey I'm having some trouble managing multiple instances of the same class in a java program. I've creating a few instances of a java class that contains a few methods that add/subtract from an integer in the class, but what's happening is that the adding and subtracting is being done on all of the instances (see code below), any tips on managing these instances is most appreciated.

Integerclass num1 = new Integerclass();
Integerclass num2 = new Integerclass();
Integerclass num3 = new Integerclass();
num1.assignvalue(3);
num2.assignvalue(5);
num1.addone();
num2.subtractone();
System.out.println(num1.i);
System.out.println(num2.i);

So what happens when I try to print out the integer 'i' from the integer class from each instance they are identical even though they should be different values since they are different instances and I was adding and subtracting different values to them.

Answer 1

Let's go through this step by step.

Integerclass num1 = new Integerclass();
Integerclass num2 = new Integerclass();

We have two new instances, num1 and num2.

num1.assignvalue(3);

num1 is now 3.

num2.assignvalue(5);

num2 is now 5.

num1.addone();

num1 is now 4.

num2.subtractone();

num2 is now 4.

System.out.println(num1.i);
System.out.println(num2.i);

Both num1 and num2 are 4 so these will print the same thing.

Your code appears to be fine. If you don't do the exact same calculations, they will print differant values.