The Visitor pattern is typically used in such cases. Although the code is a bit more complicated, but after adding a new RecordType subclass you have to implement the logic everywhere, as it won’t compile otherwise. With instanceof all over the place it is very easy to miss one or two places. Example: public abstract … Read more
You can use Class.isArray() public static boolean isArray(Object obj) { return obj!=null && obj.getClass().isArray(); } This works for both object and primitive type arrays. For toString take a look at Arrays.toString. You’ll have to check the array type and call the appropriate toString method.
If you have to do this, the only way would be the getClass().equals(Foo.class) option you’ve suggested. However, the goal of OO design is to allow you to treat any Foo in the same fashion. Whether or not the instance is a subclass should be irrelevant in a normal program.
You could compare Class#getName() or, maybe better, Class#getSimpleName() to a String. <h:link rendered=”#{model[‘class’].simpleName eq ‘ClassA’}”> #{errorMessage1} </h:link> <h:link rendered=”#{model[‘class’].simpleName eq ‘ClassB’}”> #{errorMessage2} </h:link> Note the importance of specifying Object#getClass() with brace notation [‘class’] because class is a reserved Java literal which would otherwise throw an EL exception in EL 2.2+. The type safe alternative is … Read more
You have to read the API carefully for this methods. Sometimes you can get confused very easily. It is either: if (B.class.isInstance(view)) API says: Determines if the specified Object (the parameter) is assignment-compatible with the object represented by this Class (The class object you are calling the method at) or: if (B.class.isAssignableFrom(view.getClass())) API says: Determines … Read more
There’s very little practical use for String objects as created by new String(“foo”). The only advantage a String object has over a primitive string value is that as an object it can store properties: var str = “foo”; str.prop = “bar”; alert(str.prop); // undefined var str = new String(“foo”); str.prop = “bar”; alert(str.prop); // “bar” … Read more
Old code will not work correctly The implied cast feature is justified after all but we have trouble to implement this FR to java because of backward-compatibility. See this: public class A { public static void draw(Square s){…} // with implied cast public static void draw(Object o){…} // without implied cast public static void main(String[] … Read more
Class.isInstance does what you want. if (Point.class.isInstance(someObj)){ … } Of course, you shouldn’t use it if you could use instanceof instead, but for reflection scenarios it often comes in handy.
You could implement the Visitor pattern. Detailed Answer The idea is to use polymorphism to perform the type-checking. Each subclass overrides the accept(Visitor) method, which should be declared in the superclass. When we have a situation like: void add(Vehicle vehicle) { //what type is vehicle?? } We can pass an object into a method declared … Read more
It’s definitely has its place in a stock implementation of equals. E.g. public boolean equals ( Object o ) { if ( this == o ) { return true; } if ( ! (o instanceof MyClass) ) { return false; } // Compare fields … } One neat thing to know about instanceof is that … Read more