Name: sdC67446 Date: 09/23/98


The methods equals(DataFlavor df) and equals(String df) of class
java.awt.datatransfer.DataFlavor throw NullPointerException
if 'df' == null. More consistent behaviour is to return 'false' for null
input parameters like equals(Object) does. The behaviour of
equals(Object) specified in JLS:


20.1.3 public boolean equals(Object obj)

This method indicates whether some other object is "equal to" this one.

The general contract of equals is that it implements an equivalence relation:

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

The equals method defined by class Object implements the most discriminating possible equivalence relation on objects;
that is, for any reference values x and y, ((Object)x).equals(y) returns true if and only if x and y refer to the same
object.

The doc says:
--------------------------------------------------
public boolean equals(DataFlavor dataFlavor)

      Returns:
            if the DataFlavors represent the same type.

public boolean equals(java.lang.String s)

      Returns:
            if the String (MimeType) is equal

public boolean equals(java.lang.Object o)

      Returns:
            if the objects are equal
      Overrides:
            equals in class java.lang.Object

The test demonstrating the bug:
-----------------Test.java------------------------
import java.awt.datatransfer.*;

public class Test {

    public static void main(String[] args) {
DataFlavor df = null;
try {
df = new DataFlavor("application/postscript;class=java.awt.datatransfer.DataFlavor");
} catch (ClassNotFoundException e) {
System.out.println(e);
System.exit(1);
}
try {
System.out.println(df.equals((Object)null));
} catch (Exception e) {
System.out.println(e);
}
try {
System.out.println(df.equals((String)null));
} catch (Exception e) {
System.out.println(e);
}
try {
System.out.println(df.equals((DataFlavor)null));
} catch (Exception e) {
System.out.println(e);
}
    };
}
---------Output-----------------------------------
false
java.lang.NullPointerException
java.lang.NullPointerException
--------------------------------------------------
======================================================================