Java: How to define custom Integer-based data type?

Question

I need a data type that behaves completely like Integer with this difference that I want it to overflow and underflow to certain values. On the other words, I'd like to set the MAX_VALUE and MIN_VALUE of an object/instance of the Integer class. The problem is MAX_VALUE and MIN_VALUE are constant and Integer class in final. How should I approach?

Answer 1

You'll have to create your own wrapper class:

public class CustomInteger
{
    public static final int MAX_VALUE = 5000;
    public static final int MIN_VALUE = -5000;

    private final int value;

    public CustomInteger(int value)
    {
        // TODO: Validation
        this.value = value;
    }

    // Add all the methods you want - e.g. integer operations etc
    // performing custom overflow/underflow on each operation
}

You need to decide whether you want one fixed pair of limits for the whole type, or whether each instance can have a different limit (and what that means when adding together two values with different limits etc).

Answer 2

Since java.lang.Integer is final you cannot extend it. The only choice is to wrap it:

public class LimitedInteger {
    private int value;
    private int min;
    private int max;


    LimitedInteger() {
    }
    LimitedInteger(int value) {
         this.value = value;
    }
    LimitedInteger(int value, int min, int max) {
         this.value = value;
         this.min = min;
         this.max = max;
    }
}

etc, etc