Java 变量不在 scope 中，即使我已经在 class 中声明了它？

Question

My compiler keeps saying that 'cents' in my toString method is out of scope, but I don't understand why this is because I've already declared it in the class.

Here is my code:

public class Currency
{
private Double value;

// Constructor
public Currency(Double startValue)
{
    value = startValue;
}

// Sets value to newValue
public void setValue(Double newValue)
{
    value = newValue;
}

// Returns the dollar portion of value
// if value is 12.34, returns 12
public Integer getDollars()
{
return value.intValue();
}

// Returns the cents portion of value
// as an Integer
// if value is 12.34, returns 34
public Integer getCents()
{
Integer cents = (int)(value * 100) % 100;
return cents;
}

// Returns a String representation
// in the format
// $12.34
public String toString()
{
return "$" + value + cents;
}

}

Answer 1

as you want two precision(ie format value in %.2f) for value you can consider using something like below

 // Returns a String representation in the format  $12.34
    public String toString()
    {
    return "$" + String.format("%.2f", value) ;
    }

    // main class

    public static void main(String[] a)
    {
        Currency c = new Currency(12.3423456d);
        System.out.println("Cents: "+c.getCents());

        System.out.println(c);
    }

Output: Cents: 34 $12.34

Answer 2

You declared cents inside a method, so it has function-scope. You need to declare it on class level like you did with value.

private Double value;
private int cents;

In your method you can call it like this:

cents = (int)(value * 100) % 100;

That would solve your technical problem. Some people would say that's not right because you are calculating cents directly from value. Others will say it's fine. In the end it depends how often you are calling the function if you calculate it. In some cases it will be better to have it in an extra variable.

Changing the code like shown above will solve the technical problem you asked for.