DoubleInsertException.java

codice:
package org.gengi.exceptions;

public class DoubleInsertException extends Exception{

    private Object value;

    public DoubleInsertException(Object value) {
        this.value = value;
    }

    @Override
    public String toString() {
        return "DoubleInsertExecption: double insert of value " + value.toString();
    }
}
Demo:

codice:
package org.gengi.exceptions;

import java.util.ArrayList;
import java.util.List;

public class Demo {

    static List<Integer> values = new ArrayList<Integer>();

    static void insert(int number) throws DoubleInsertException{

        if(values.contains(number)){

            throw new DoubleInsertException(number);
        }

        values.add(number);
    }

    public static void main(String[] args){
        try {
            insert(1);
            insert(1);
        }

        catch (DoubleInsertException ex) {
            ex.printStackTrace();
        }
    }
}
ecco a te.

Gengi