[LANG-1113] Manages Comparable in EqualsBuilder

• Type: New Feature
• Status: Open
• Priority: Trivial
• Resolution: Unresolved
• Fix Version/s: Discussion
• Component/s: lang.builder.*
• Labels: BigDecimal EqualsBuilder
• Assignee: Unassigned
• Reporter: Simon Meyffret
• Created: 10/Apr/15 18:43
• Updated: 27/May/15 14:48

Description

As explained by LANG-393 and LANG-467, EqualsBuilder fails to provide a proper way to handle BigDecimal since BigDecimal takes the scale into account when using equals() but not with compareTo().

Would it be possible to add a method appendComparable() in EqualsBuilder to manages Comparable objects when we want to build equality on compareTo() and not equals()?

Making clear that EqualsBuilder is not compliant with HashCodeBuilder when using this method.

For example:

    return new EqualsBuilder()
        .append(this.name, other.name)
        .appendComparable(this.amount, other.amount)
        .isEqual();

with:

EqualsBuilder.java

	/**
	 * <p>Test if two <code>Comparable</code>s are equal using their
	 * <code>compareTo</code> method.</p>
	 * <p>This may break the <code>equals</code>/<code>hashcode</code> contract but
	 * it is useful in some situation, specially with {@link java.math.BigDecimal}.</p>
	 * 
	 * @param lhs  the left hand comparable
	 * @param rhs  the right hand comparable
	 * @return EqualsBuilder - used to chain calls.
	 */
	public <T extends Comparable<? super T>> EqualsBuilder appendComparable(T lhs, T rhs) {
		if (isEquals == false) {
			return this;
		}
		if (lhs == rhs) {
			return this;
		}
		if (lhs == null || rhs == null) {
			isEquals = false;
			return this;
		} else if (lhs.compareTo(rhs) != 0) {
			isEquals = false;
			return this;
		}
		return this;
	}
	
	/**
	 * <p>Performs a deep comparison of two <code>Comparable</code> arrays.</p>
	 * 
	 * @param lhs  the left hand <code>Comparable[]</code>
	 * @param rhs  the right hand <code>Comparable[]</code>
	 * @return EqualsBuilder - used to chain calls.
	 * @see #appendComparable(Comparable, Comparable)
	 */
	public <T extends Comparable<? super T>> EqualsBuilder appendComparable(T[] lhs, T[] rhs) {
		if (isEquals == false) {
			return this;
		}
		if (lhs == rhs) {
			return this;
		}
		if (lhs == null || rhs == null) {
			isEquals = false;
			return this;
		}
		if (lhs.length != rhs.length) {
			isEquals = false;
			return this;
		}
		for (int i = 0; i < lhs.length && isEquals; ++i) {
			appendComparable(lhs[i], rhs[i]);
		}
		return this;
	}

Issue Links

• is related to: LANG-467 EqualsBuilder and HashCodeBuilder treat java.math.BigDecimal inconsistantly and break general contract of hashCode
• is related to: LANG-393 EqualsBuilder don't compare BigDecimals correctly