Test if object implements interface

This has probably been asked before, but a quick search only brought up the same question asked for C#. See here.

What I basically want to do is to check wether a given object implements a given interface.

I kind of figured out a solution but this is just not comfortable enough to use it frequently in if or case statements and I was wondering wether Java does not have built-in solution.

public static Boolean implementsInterface(Object object, Class interf){
    for (Class c : object.getClass().getInterfaces()) {
        if (c.equals(interf)) {
            return true;
        }
    }
    return false;
}

The instanceof operator does the work in a NullPointerException safe way. For example:

 if ("" instanceof java.io.Serializable) {
     // it's true
 }

yields true. Since:

 if (null instanceof AnyType) {
     // never reached
 }

yields false, the instanceof operator is null safe (the code you posted isn't).

instanceof is the built-in, compile-time safe alternative to Class#isInstance(Object)

This should do:

public static boolean implementsInterface(Object object, Class interf){
    return interf.isInstance(object);
}

For example,

 java.io.Serializable.class.isInstance("a test string")

evaluates to true.

I prefer instanceof:

if (obj instanceof SomeType) { ... }

which is much more common and readable than SomeType.isInstance(obj)

that was easy :

   interf.isInstance(object)

If you want to test for interfaces:

public List<myType> getElement(Class<?> clazz) {
    List<myType> els = new ArrayList<myType>();
    for (myType e: this.elements.values()) {
        if (clazz.isAssignableFrom(e.getClass())) {
            els.add(e);
        }
    }
    return els;

}

clazz is an Interface and myType is a Type that you defined that may implement a number of interfaces. With this code you get only the types that implement a defined interface