1.1 --- /dev/null	Thu Jan 01 00:00:00 1970 +0000
     1.2 +++ b/samples/cloneproblem/src/org/apidesign/cloneproblem/Interval.java	Tue Mar 01 21:28:39 2011 +0100
     1.3 @@ -0,0 +1,44 @@
     1.4 +package org.apidesign.cloneproblem;
     1.5 +
     1.6 +import java.util.Date;
     1.7 +
     1.8 +// BEGIN: interval.api
     1.9 +/** Quiz: Anyone can come up with a JUnit test to generate
    1.10 + * {@link NullPointerException} directly from the code of 
    1.11 + * the <code>Interval</code> class?
    1.12 + *
    1.13 + * @author Jaroslav Tulach <jaroslav.tulach@apidesign.org>
    1.14 + */
    1.15 +public final class Interval {
    1.16 +    private final Date from, to;
    1.17 +    
    1.18 +    /** Constructs interval between two dates.
    1.19 +     * 
    1.20 +     * @param from the 'sooner' date
    1.21 +     * @param to the 'later' date
    1.22 +     * @throws IllegalArgumentException if <code>from</code> is not less then <code>to</code>
    1.23 +     */
    1.24 +    public Interval(Date from, Date to) {
    1.25 +        if (from == null) {
    1.26 +            throw new IllegalArgumentException("'from' cannot be null!");
    1.27 +        }
    1.28 +        if (to == null) {
    1.29 +            throw new IllegalArgumentException("'to' cannot be null!");
    1.30 +        }
    1.31 +        // shield us from Date's mutability
    1.32 +        this.from = (Date) from.clone();
    1.33 +        this.to = (Date)to.clone();
    1.34 +        if (from.compareTo(to) >= 0) {
    1.35 +            throw new IllegalArgumentException("'from' must be lower than 'to'!");
    1.36 +        }
    1.37 +    }
    1.38 +    
    1.39 +    /** The length of the interval in milliseconds 
    1.40 +     * 
    1.41 +     * @return amount of milliseconds between 'from' and 'to' dates.
    1.42 +     */
    1.43 +    public long getLength() {
    1.44 +        return to.getTime() - from.getTime();
    1.45 +    }
    1.46 +}
    1.47 +// END: interval.api