ClassUtils

Utilities for Class objects are available in ClassUtils. This page lists a few of the features.

Class loading

Classes can be loaded and checked for existence with ClassUtils#classExists, ClassUtils#tryLoadClass and ClassUtils#loadClassOrThrow. These methods exist as wrappers around Class#forName and are added for convenience so you don't have to deal with the checked exceptions.

Class name

ClassUtils#getClassName allows you to get the class name null-safely. To get a short, user-friendly name for all classes, you can use ClassUtils#getSemanticName. This method is intended as an alternative to Class#getSimpleName, which sometimes produces no output, or output that makes it impossible to identify the class even for humans.

Class	Class#getSimpleName	ClassUtils#getSemanticName
int[].class	"int[]"	"int[]"
Map.Entry.class	"Entry"	"Map$Entry"
new Object() { }.getClass()	"" (empty string)	"ParentClass$1"
null	NPE	"null"

As subclass

Avoid checked errors by using ClassUtils#asSubclassIfPossible:

void storeClass(Class<? extends Serializable> clazz) { ... }

ClassUtils.asSubclassIfPossible(clazz, Serializable.class)
          .ifPresent(subclass -> storeClass(subclass));

Plain Java:

if (Serializable.class.isAssignableFrom(clazz)) {
    storeClass((Class) clazz); // Unchecked warning
}

Note: to find out if a class is an enum, use EnumUtils#asEnumClassIfPossible instead.

Class type

ClassUtils#getType(Class) returns an entry of the enum ClassType to describe what kind of class was input: e.g., ClassUtils.getType(Serializable.class) returns INTERFACE, ClassUtils.getType(Override.class) returns ANNOTATION. Before you inspect a class, you may want to make sure that a class is of the desired type.

To process classes differently based on their type, you can use ClassUtils#processClassByType. It takes a ClassTypeCallback that you implement, where you can define behavior for each class type:

ClassTypeCallback<String> callback = new ClassTypeCallback<String>() {
    @Override
    public String forEnum(Class<? extends Enum<?>> enumClass) {
        return "enum[" + enumClass.getSimpleName() + "]";
    }

    @Override
    public String forAnnotation(Class<? extends Annotation> annotationClass) {
        return "@" + annotationClass.getSimpleName();
    }
};

System.out.println(ClassUtils.processClassByType(TimeUnit.class, callback)); // enum[TimeUnit]
System.out.println(ClassUtils.processClassByType(Override.class, callback)); // @Override
System.out.println(ClassUtils.processClassByType(int[].class, callback));    // null (method for ARRAY not overridden)