[PDFBOX-5724] CharStringCommand.equals() does not conform to the contract of Object.equals

• Type: Bug
• Status: Closed
• Priority: Critical
• Resolution: Fixed
• Affects Version/s: 3.0.1 PDFBox, 4.0.0
• Fix Version/s: 3.0.2 PDFBox, 4.0.0
• Component/s: FontBox
• Assignee: Tilman Hausherr
• Reporter: Axel Howind
• Created: 03/Dec/23 05:04
• Updated: 14/Mar/24 20:57
• Resolved: 04/Dec/23 07:23

Description

The equals() method in CharStringCommand breaks the contract of Object.equals(). From the Object.equals() Javadoc:
 

The equals method implements an equivalence relation on non-null object references:

• It is reflexive: for any non-null reference value x, x.equals should return true.
• It is symmetric: for any non-null reference values x and y, x.equals should return true if and only if y.equals returns true.
• It is transitive: for any non-null reference values x, y, and z, if x.equals returns true and y.equals(z) returns true, then x.equals(z) should return true.
• It is consistent: for any non-null reference values x and y, multiple invocations of x.equals consistently return true or consistently return false, provided no information used in equals comparisons on the objects is modified.
• For any non-null reference value x, x.equals(null) should return false.

This is the current implementation:

    @Override
    public boolean equals(Object object)
    {
        if (object instanceof CharStringCommand)
        {
            CharStringCommand that = (CharStringCommand) object;
            if (type1KeyWord != null && type1KeyWord == that.getType1KeyWord())
            {
                return true;
            }
            if (type2KeyWord != null && type2KeyWord == that.getType2KeyWord())
            {
                return true;
            }
            if (type1KeyWord == null && type2KeyWord == null)
            {
                return true;
            }
        }
        return false;
    }

If type1Keyword==null and type2Keyword!=null, true is returned without checking the values of that.getType1Keyword() and that.getType2Keyword().

Now imagine a has both fields set to null and b has not. Then a.equals(b)==true and b.equals(a)!=true.