doubt: equals&==

[Scott Xia]

given:
Float f2 = new Float("10F");
Double d1 = new Double("10D");
System.out.println(10F==10D); // return true
System.out.println(f2.equals(d1)); // return false
what the equals method of Float class do ? i do not understand.
can you tell me ?

[chetna_jain]

equals method checks whether both points towards same location or not.
i am not sure whether i am right but still i am replying pls correct me if i am wrong

[Angela Narain]

If the class overrides the equals() method of Object class
( i.e. the String, File, Date , BitSet and the wrapper classes )
then equals() will compare the contents and == is
for comparing the object reference.

Correct me if wrong

[vipin bhatia]

equals method takes in a object but will return true only if the input parameter is a float & has the same value as the float object whose equals method is being called i.e
Float f1 = new Float(10.0f);
Float f2 = new Float(10.0f);
Double d1 = new Double(10.0);
f1.equals(f2) returns true,
f1.equals(d1) returns false,
f1==f2 returns false as f1 & f2 point to different objects & == only checks if the two object references refer to same object & does not care to check the value stored int he object being referenced
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Sun Certified Programmer for Java2 Platform scored 100%.

[chetna_jain]

i am not clear with the difference between them

[marilyn murphy]

Originally posted by Scott Xia:
given:
Float f2 = new Float("10F");
Double d1 = new Double("10D");
System.out.println(10F==10D); // return true
System.out.println(f2.equals(d1)); // return false
what the equals method of Float class do ? i do not understand.
can you tell me ?

Float != Double just like String != Float

equals() method of the Float class compares one Float with another Float to see if they are equal value. If you want to compare the Float value with the Double value, you need to extract the values.

[galen wang]

from jdk api definition of Class Float:
public boolean equals(Object obj)
Compares this object against the specified object. The result is true if and only if the argument is not null and is a Float object that represents a float with the same value as the float represented by this object. For this purpose, two float values are considered to be the same if and only if the method floatToIntBits(float) returns the identical int value when applied to each.
Note that in most cases, for two instances of class Float, f1 and f2, the value of f1.equals(f2) is true if and only if
f1.floatValue() == f2.floatValue()

also has the value true. However, there are two exceptions:
1) If f1 and f2 both represent Float.NaN, then the equals method returns true, even though Float.NaN==Float.NaN has the value false.
2) If f1 represents .0f while f2 represents -0.0f, or vice versa, the equal test has the value false, even though 0.0f==-0.0f has the value true.

[This message has been edited by galen wang (edited September 21, 2001).]

[Scott Xia]

thank you all