Why does Stack
in Java have an empty()
method along with the usual isEmpty()
? All abstract classes that Stack
extends have an isEmpty()
method.
isEmpty() method in Java is used to check and verify if a Stack is empty or not. It returns True if the Stack is empty else it returns False. Syntax: Stack.isEmpty() Parameters: This method does not take any parameter.
Both methods are used to check for blank or empty strings in java. The difference between both methods is that isEmpty() method returns true if, and only if, string length is 0.
empty() method in Java is used to check whether a stack is empty or not. The method is of boolean type and returns true if the stack is empty else false. Parameters: The method does not take any parameters. Return Value: The method returns boolean true if the stack is empty else it returns false.
I believe OP's question is more on : why there are duplicated methods, given empty()
and isEmpty()
are doing the same thing?
If you take a closer look, in Vector
, Stack
and HashTable
, there are more examples of methods doing similar thing with different names.
Here is the brief history:
At the time of JDK 1.0, there was no "Collection" framework in Java. Stack
, Vector
, HashTable
were some of the basic data structures provided by Java.
Later in JDK 1.2, Collection framework was added to JDK, and standard interfaces (like List
, Map
) were introduced.
However in these new standard collection interfaces, methods were named in a different convention. The change in naming convention was most probably influenced by Java Bean standard introduced also in JDK 1.2. These method names were different from those in old Stack
, Vector
and HashTable
classes. For example, it was named empty()
in original class but was named isEmpty()
of Collection
interface.
In order to make Stack
, Vector
and HashTable
compatible with Collection framework, Stack
, Vector
and HashTable
has implemented its corresponding Collection interfaces. On the same time, old methods were kept for the sake of backward compatibility.
Hence the "duplicated" methods you see now.
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