I m looking at some Java code, and there is this code that I see often.
Foo.class
This is being used to to indicate the Type of the class? is that similar to
Foo.GetType();
typeof(Foo);
in C# ?
What is it being used for ? and what s the meaning of it?
Yes, Foo.class
in Java is equivalent to typeof(Foo)
in C#. See section 15.8.2 of the JLS for more information on class literals .
It's not the same as calling GetType()
on a reference, which gets the execution time type of an object. The Java equivalent of that is someReference.getClass()
.
One reason you may see it more often in Java code than in C# is in relation to generics. It's not entirely unusual to have something like:
public class Generic<T>
{
private final Class<T> clazz;
public Generic(Class<T> clazz)
{
this.clazz = clazz;
}
}
This allows execution-time access to the class for reflection etc. This is only necessary in Java due to type erasure , whereby an object of a generic type can't normally determine its type arguments at execution time.
there is special class in java called Class . it inherits Object . its instance represents the classes and interfaces in java runtime, and also represents enum、array、primitive Java types(boolean, byte, char, short, int, long, float, double)and the key word void . when a class is loaded, or the method defineClass() of class loader is called by JVM, then JVM creates a Class object.
Java allows us to create a corresponding Class object of a class in many ways, and .class is one of them. eg
Class c1 = String.class;
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