Class java.lang.reflect.Method - JDK 5 Documentation v1.1.8, Java 2 SDK 英文文档

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Class java.lang.reflect.Method

java.lang.Object
   |
   +----java.lang.reflect.Method

public final class Method
extends Object
implements Member

A Method provides information about, and access to, a single method on a class or interface. The reflected method may be a class method or an instance method (including an abstract method).

A Method permits widening conversions to occur when matching the actual parameters to invokewith the underlying method's formal parameters, but it throws an IllegalArgumentException if a narrowing conversion would occur.

See Also:: Member, Class, getMethods, getMethod, getDeclaredMethods, getDeclaredMethod

equals(Object): Compares this Method against the specified object.
getDeclaringClass(): Returns the Class object representing the class or interface that declares the method represented by this Method object.
getExceptionTypes(): Returns an array of Class objects that represent the types of the checked exceptions thrown by the underlying method represented by this Method object.
getModifiers(): Returns the Java language modifiers for the method represented by this Method object, as an integer.
getName(): Returns the name of the method represented by this Method object, as a String.
getParameterTypes(): Returns an array of Class objects that represent the formal parameter types, in declaration order, of the method represented by this Method object.
getReturnType(): Returns a Class object that represents the formal return type of the method represented by this Method object.
hashCode(): Returns a hashcode for this Method.
invoke(Object, Object[]): Invokes the underlying method represented by this Method object, on the specified object with the specified parameters.
toString(): Returns a string describing this Method.

getDeclaringClass

 public Class getDeclaringClass()

Returns the Class object representing the class or interface that declares the method represented by this Method object.

getName

 public String getName()

Returns the name of the method represented by this Method object, as a String.

getModifiers

 public native int getModifiers()

Returns the Java language modifiers for the method represented by this Method object, as an integer. The Modifier class should be used to decode the modifiers.

See Also:: Modifier

getReturnType

 public Class getReturnType()

Returns a Class object that represents the formal return type of the method represented by this Method object.

getParameterTypes

 public Class[] getParameterTypes()

Returns an array of Class objects that represent the formal parameter types, in declaration order, of the method represented by this Method object. Returns an array of length 0 if the underlying method takes no parameters.

getExceptionTypes

 public Class[] getExceptionTypes()

Returns an array of Class objects that represent the types of the checked exceptions thrown by the underlying method represented by this Method object. Returns an array of length 0 if the method throws no checked exceptions.

equals

 public boolean equals(Object obj)

Compares this Method against the specified object. Returns true if the objects are the same. Two Methods are the same if they were declared by the same class and have the same name and formal parameter types.

Overrides:: equals in class Object

hashCode

 public int hashCode()

Returns a hashcode for this Method. The hashcode is computed as the exclusive-or of the hashcodes for the underlying method's declaring class name and the method's name.

Overrides:: hashCode in class Object

toString

 public String toString()

Returns a string describing this Method. The string is formatted as the method access modifiers, if any, followed by the method return type, followed by a space, followed by the class declaring the method, followed by a period, followed by the method name, followed by a parenthesized, comma-separated list of the method's formal parameter types. If the method throws checked exceptions, the parameter list is followed by a space, followed by the word throws followed by a comma-separated list of the thrown exception types. For example:

    public boolean java.lang.Object.equals(java.lang.Object)

The access modifiers are placed in canonical order as specified by "The Java Language Specification". This is public, protected or private first, and then other modifiers in the following order: abstract, static, final, synchronized native.

Overrides:: toString in class Object

invoke

 public native Object invoke(Object obj,
                             Object args[]) throws IllegalAccessException, IllegalArgumentException, InvocationTargetException

Invokes the underlying method represented by this Method object, on the specified object with the specified parameters. Individual parameters are automatically unwrapped to match primitive formal parameters, and both primitive and reference parameters are subject to widening conversions as necessary. The value returned by the underlying method is automatically wrapped in an object if it has a primitive type.

Method invocation proceeds with the following steps, in order:

If the underlying method is static, then the specified object argument is ignored. It may be null.

Otherwise, the method is an instance method. If the specified object argument is null, the invocation throws a NullPointerException. Otherwise, if the specified object argument is not an instance of the class or interface declaring the underlying method, the invocation throws an IllegalArgumentException.

If this Method object enforces Java language access control and the underlying method is inaccessible, the invocation throws an IllegalAccessException.

If the number of actual parameters supplied via args is different from the number of formal parameters required by the underlying method, the invocation throws an IllegalArgumentException.

For each actual parameter in the supplied args array:

If the corresponding formal parameter has a primitive type, an unwrapping conversion is attempted to convert the object value to a value of a primitive type. If this attempt fails, the invocation throws an IllegalArgumentException.

If, after possible unwrapping, the parameter value cannot be converted to the corresponding formal parameter type by an identity or widening conversion, the invocation throws an IllegalArgumentException.

If the underlying method is an instance method, it is invoked using dynamic method lookup as documented in The Java Language Specification, section 15.11.4.4; in particular, overriding based on the runtime type of the target object will occur.

If the underlying method is static, it is invoked as exactly the method on the declaring class.

Control transfers to the underlying method. If the method completes abruptly by throwing an exception, the exception is placed in an InvocationTargetException and thrown in turn to the caller of invoke.

If the method completes normally, the value it returns is returned to the caller of invoke; if the value has a primitive type, it is first appropriately wrapped in an object. If the underlying method return type is void, the invocation returns null.

Throws: IllegalAccessException: if the underlying method is inaccessible.
Throws: IllegalArgumentException: if the number of actual and formal parameters differ, or if an unwrapping conversion fails.
Throws: InvocationTargetException: if the underlying method throws an exception.
Throws: NullPointerException: if the specified object is null.

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