Class ClassUtils

java.lang.Object
org.apache.commons.lang.ClassUtils

public class ClassUtils extends Object

Operates on classes without using reflection.

This class handles invalid null inputs as best it can. Each method documents its behaviour in more detail.

The notion of a canonical name includes the human readable name for the type, for example int[]. The non-canonical method variants work with the JVM names, such as [I.

Since:
2.0
Version:
$Id: ClassUtils.java 1057072 2011-01-10 01:55:57Z niallp $
  • Field Details

    • PACKAGE_SEPARATOR_CHAR

      public static final char PACKAGE_SEPARATOR_CHAR

      The package separator character: '.' == '.'.

      See Also:
    • PACKAGE_SEPARATOR

      public static final String PACKAGE_SEPARATOR

      The package separator String: ".".

    • INNER_CLASS_SEPARATOR_CHAR

      public static final char INNER_CLASS_SEPARATOR_CHAR

      The inner class separator character: '$' == '$'.

      See Also:
    • INNER_CLASS_SEPARATOR

      public static final String INNER_CLASS_SEPARATOR

      The inner class separator String: "$".

  • Constructor Details

    • ClassUtils

      public ClassUtils()

      ClassUtils instances should NOT be constructed in standard programming. Instead, the class should be used as ClassUtils.getShortClassName(cls).

      This constructor is public to permit tools that require a JavaBean instance to operate.

  • Method Details

    • getShortClassName

      public static String getShortClassName(Object object, String valueIfNull)

      Gets the class name minus the package name for an Object.

      Parameters:
      object - the class to get the short name for, may be null
      valueIfNull - the value to return if null
      Returns:
      the class name of the object without the package name, or the null value
    • getShortClassName

      public static String getShortClassName(Class cls)

      Gets the class name minus the package name from a Class.

      Parameters:
      cls - the class to get the short name for.
      Returns:
      the class name without the package name or an empty string
    • getShortClassName

      public static String getShortClassName(String className)

      Gets the class name minus the package name from a String.

      The string passed in is assumed to be a class name - it is not checked.

      Parameters:
      className - the className to get the short name for
      Returns:
      the class name of the class without the package name or an empty string
    • getPackageName

      public static String getPackageName(Object object, String valueIfNull)

      Gets the package name of an Object.

      Parameters:
      object - the class to get the package name for, may be null
      valueIfNull - the value to return if null
      Returns:
      the package name of the object, or the null value
    • getPackageName

      public static String getPackageName(Class cls)

      Gets the package name of a Class.

      Parameters:
      cls - the class to get the package name for, may be null.
      Returns:
      the package name or an empty string
    • getPackageName

      public static String getPackageName(String className)

      Gets the package name from a String.

      The string passed in is assumed to be a class name - it is not checked.

      If the class is unpackaged, return an empty string.

      Parameters:
      className - the className to get the package name for, may be null
      Returns:
      the package name or an empty string
    • getAllSuperclasses

      public static List getAllSuperclasses(Class cls)

      Gets a List of superclasses for the given class.

      Parameters:
      cls - the class to look up, may be null
      Returns:
      the List of superclasses in order going up from this one null if null input
    • getAllInterfaces

      public static List getAllInterfaces(Class cls)

      Gets a List of all interfaces implemented by the given class and its superclasses.

      The order is determined by looking through each interface in turn as declared in the source file and following its hierarchy up. Then each superclass is considered in the same way. Later duplicates are ignored, so the order is maintained.

      Parameters:
      cls - the class to look up, may be null
      Returns:
      the List of interfaces in order, null if null input
    • convertClassNamesToClasses

      public static List convertClassNamesToClasses(List classNames)

      Given a List of class names, this method converts them into classes.

      A new List is returned. If the class name cannot be found, null is stored in the List. If the class name in the List is null, null is stored in the output List.

      Parameters:
      classNames - the classNames to change
      Returns:
      a List of Class objects corresponding to the class names, null if null input
      Throws:
      ClassCastException - if classNames contains a non String entry
    • convertClassesToClassNames

      public static List convertClassesToClassNames(List classes)

      Given a List of Class objects, this method converts them into class names.

      A new List is returned. null objects will be copied into the returned list as null.

      Parameters:
      classes - the classes to change
      Returns:
      a List of class names corresponding to the Class objects, null if null input
      Throws:
      ClassCastException - if classes contains a non-Class entry
    • isAssignable

      public static boolean isAssignable(Class[] classArray, Class[] toClassArray)

      Checks if an array of Classes can be assigned to another array of Classes.

      This method calls isAssignable for each Class pair in the input arrays. It can be used to check if a set of arguments (the first parameter) are suitably compatible with a set of method parameter types (the second parameter).

      Unlike the Class.isAssignableFrom(java.lang.Class) method, this method takes into account widenings of primitive classes and nulls.

      Primitive widenings allow an int to be assigned to a long, float or double. This method returns the correct result for these cases.

      Null may be assigned to any reference type. This method will return true if null is passed in and the toClass is non-primitive.

      Specifically, this method tests whether the type represented by the specified Class parameter can be converted to the type represented by this Class object via an identity conversion widening primitive or widening reference conversion. See The Java Language Specification, sections 5.1.1, 5.1.2 and 5.1.4 for details.

      Parameters:
      classArray - the array of Classes to check, may be null
      toClassArray - the array of Classes to try to assign into, may be null
      Returns:
      true if assignment possible
    • isAssignable

      public static boolean isAssignable(Class[] classArray, Class[] toClassArray, boolean autoboxing)

      Checks if an array of Classes can be assigned to another array of Classes.

      This method calls isAssignable for each Class pair in the input arrays. It can be used to check if a set of arguments (the first parameter) are suitably compatible with a set of method parameter types (the second parameter).

      Unlike the Class.isAssignableFrom(java.lang.Class) method, this method takes into account widenings of primitive classes and nulls.

      Primitive widenings allow an int to be assigned to a long, float or double. This method returns the correct result for these cases.

      Null may be assigned to any reference type. This method will return true if null is passed in and the toClass is non-primitive.

      Specifically, this method tests whether the type represented by the specified Class parameter can be converted to the type represented by this Class object via an identity conversion widening primitive or widening reference conversion. See The Java Language Specification, sections 5.1.1, 5.1.2 and 5.1.4 for details.

      Parameters:
      classArray - the array of Classes to check, may be null
      toClassArray - the array of Classes to try to assign into, may be null
      autoboxing - whether to use implicit autoboxing/unboxing between primitives and wrappers
      Returns:
      true if assignment possible
      Since:
      2.5
    • isAssignable

      public static boolean isAssignable(Class cls, Class toClass)

      Checks if one Class can be assigned to a variable of another Class.

      Unlike the Class.isAssignableFrom(java.lang.Class) method, this method takes into account widenings of primitive classes and nulls.

      Primitive widenings allow an int to be assigned to a long, float or double. This method returns the correct result for these cases.

      Null may be assigned to any reference type. This method will return true if null is passed in and the toClass is non-primitive.

      Specifically, this method tests whether the type represented by the specified Class parameter can be converted to the type represented by this Class object via an identity conversion widening primitive or widening reference conversion. See The Java Language Specification, sections 5.1.1, 5.1.2 and 5.1.4 for details.

      Parameters:
      cls - the Class to check, may be null
      toClass - the Class to try to assign into, returns false if null
      Returns:
      true if assignment possible
    • isAssignable

      public static boolean isAssignable(Class cls, Class toClass, boolean autoboxing)

      Checks if one Class can be assigned to a variable of another Class.

      Unlike the Class.isAssignableFrom(java.lang.Class) method, this method takes into account widenings of primitive classes and nulls.

      Primitive widenings allow an int to be assigned to a long, float or double. This method returns the correct result for these cases.

      Null may be assigned to any reference type. This method will return true if null is passed in and the toClass is non-primitive.

      Specifically, this method tests whether the type represented by the specified Class parameter can be converted to the type represented by this Class object via an identity conversion widening primitive or widening reference conversion. See The Java Language Specification, sections 5.1.1, 5.1.2 and 5.1.4 for details.

      Parameters:
      cls - the Class to check, may be null
      toClass - the Class to try to assign into, returns false if null
      autoboxing - whether to use implicit autoboxing/unboxing between primitives and wrappers
      Returns:
      true if assignment possible
      Since:
      2.5
    • primitiveToWrapper

      public static Class primitiveToWrapper(Class cls)

      Converts the specified primitive Class object to its corresponding wrapper Class object.

      NOTE: From v2.2, this method handles Void.TYPE, returning Void.TYPE.

      Parameters:
      cls - the class to convert, may be null
      Returns:
      the wrapper class for cls or cls if cls is not a primitive. null if null input.
      Since:
      2.1
    • primitivesToWrappers

      public static Class[] primitivesToWrappers(Class[] classes)

      Converts the specified array of primitive Class objects to an array of its corresponding wrapper Class objects.

      Parameters:
      classes - the class array to convert, may be null or empty
      Returns:
      an array which contains for each given class, the wrapper class or the original class if class is not a primitive. null if null input. Empty array if an empty array passed in.
      Since:
      2.1
    • wrapperToPrimitive

      public static Class wrapperToPrimitive(Class cls)

      Converts the specified wrapper class to its corresponding primitive class.

      This method is the counter part of primitiveToWrapper(). If the passed in class is a wrapper class for a primitive type, this primitive type will be returned (e.g. Integer.TYPE for Integer.class). For other classes, or if the parameter is null, the return value is null.

      Parameters:
      cls - the class to convert, may be null
      Returns:
      the corresponding primitive type if cls is a wrapper class, null otherwise
      Since:
      2.4
      See Also:
    • wrappersToPrimitives

      public static Class[] wrappersToPrimitives(Class[] classes)

      Converts the specified array of wrapper Class objects to an array of its corresponding primitive Class objects.

      This method invokes wrapperToPrimitive() for each element of the passed in array.

      Parameters:
      classes - the class array to convert, may be null or empty
      Returns:
      an array which contains for each given class, the primitive class or null if the original class is not a wrapper class. null if null input. Empty array if an empty array passed in.
      Since:
      2.4
      See Also:
    • isInnerClass

      public static boolean isInnerClass(Class cls)

      Is the specified class an inner class or static nested class.

      Parameters:
      cls - the class to check, may be null
      Returns:
      true if the class is an inner or static nested class, false if not or null
    • getClass

      public static Class getClass(ClassLoader classLoader, String className, boolean initialize) throws ClassNotFoundException
      Returns the class represented by className using the classLoader. This implementation supports the syntaxes "java.util.Map.Entry[]", "java.util.Map$Entry[]", "[Ljava.util.Map.Entry;", and "[Ljava.util.Map$Entry;".
      Parameters:
      classLoader - the class loader to use to load the class
      className - the class name
      initialize - whether the class must be initialized
      Returns:
      the class represented by className using the classLoader
      Throws:
      ClassNotFoundException - if the class is not found
    • getClass

      public static Class getClass(ClassLoader classLoader, String className) throws ClassNotFoundException
      Returns the (initialized) class represented by className using the classLoader. This implementation supports the syntaxes "java.util.Map.Entry[]", "java.util.Map$Entry[]", "[Ljava.util.Map.Entry;", and "[Ljava.util.Map$Entry;".
      Parameters:
      classLoader - the class loader to use to load the class
      className - the class name
      Returns:
      the class represented by className using the classLoader
      Throws:
      ClassNotFoundException - if the class is not found
    • getClass

      public static Class getClass(String className) throws ClassNotFoundException
      Returns the (initialized) class represented by className using the current thread's context class loader. This implementation supports the syntaxes "java.util.Map.Entry[]", "java.util.Map$Entry[]", "[Ljava.util.Map.Entry;", and "[Ljava.util.Map$Entry;".
      Parameters:
      className - the class name
      Returns:
      the class represented by className using the current thread's context class loader
      Throws:
      ClassNotFoundException - if the class is not found
    • getClass

      public static Class getClass(String className, boolean initialize) throws ClassNotFoundException
      Returns the class represented by className using the current thread's context class loader. This implementation supports the syntaxes "java.util.Map.Entry[]", "java.util.Map$Entry[]", "[Ljava.util.Map.Entry;", and "[Ljava.util.Map$Entry;".
      Parameters:
      className - the class name
      initialize - whether the class must be initialized
      Returns:
      the class represented by className using the current thread's context class loader
      Throws:
      ClassNotFoundException - if the class is not found
    • getPublicMethod

      public static Method getPublicMethod(Class cls, String methodName, Class[] parameterTypes) throws SecurityException, NoSuchMethodException

      Returns the desired Method much like Class.getMethod, however it ensures that the returned Method is from a public class or interface and not from an anonymous inner class. This means that the Method is invokable and doesn't fall foul of Java bug 4071957).

      Set set = Collections.unmodifiableSet(...);
        Method method = ClassUtils.getPublicMethod(set.getClass(), "isEmpty",  new Class[0]);
        Object result = method.invoke(set, new Object[]);

      Parameters:
      cls - the class to check, not null
      methodName - the name of the method
      parameterTypes - the list of parameters
      Returns:
      the method
      Throws:
      NullPointerException - if the class is null
      SecurityException - if a a security violation occured
      NoSuchMethodException - if the method is not found in the given class or if the metothod doen't conform with the requirements
    • toClass

      public static Class[] toClass(Object[] array)

      Converts an array of Object in to an array of Class objects. If any of these objects is null, a null element will be inserted into the array.

      This method returns null for a null input array.

      Parameters:
      array - an Object array
      Returns:
      a Class array, null if null array input
      Since:
      2.4
    • getShortCanonicalName

      public static String getShortCanonicalName(Object object, String valueIfNull)

      Gets the canonical name minus the package name for an Object.

      Parameters:
      object - the class to get the short name for, may be null
      valueIfNull - the value to return if null
      Returns:
      the canonical name of the object without the package name, or the null value
      Since:
      2.4
    • getShortCanonicalName

      public static String getShortCanonicalName(Class cls)

      Gets the canonical name minus the package name from a Class.

      Parameters:
      cls - the class to get the short name for.
      Returns:
      the canonical name without the package name or an empty string
      Since:
      2.4
    • getShortCanonicalName

      public static String getShortCanonicalName(String canonicalName)

      Gets the canonical name minus the package name from a String.

      The string passed in is assumed to be a canonical name - it is not checked.

      Parameters:
      canonicalName - the class name to get the short name for
      Returns:
      the canonical name of the class without the package name or an empty string
      Since:
      2.4
    • getPackageCanonicalName

      public static String getPackageCanonicalName(Object object, String valueIfNull)

      Gets the package name from the canonical name of an Object.

      Parameters:
      object - the class to get the package name for, may be null
      valueIfNull - the value to return if null
      Returns:
      the package name of the object, or the null value
      Since:
      2.4
    • getPackageCanonicalName

      public static String getPackageCanonicalName(Class cls)

      Gets the package name from the canonical name of a Class.

      Parameters:
      cls - the class to get the package name for, may be null.
      Returns:
      the package name or an empty string
      Since:
      2.4
    • getPackageCanonicalName

      public static String getPackageCanonicalName(String canonicalName)

      Gets the package name from the canonical name.

      The string passed in is assumed to be a canonical name - it is not checked.

      If the class is unpackaged, return an empty string.

      Parameters:
      canonicalName - the canonical name to get the package name for, may be null
      Returns:
      the package name or an empty string
      Since:
      2.4