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 package java.lang.invoke;

 import java.lang.reflect.*;

 import java.util.*;

 import java.lang.invoke.MethodHandleNatives.Constants;

 import java.lang.invoke.MethodHandles.Lookup;

 import static java.lang.invoke.MethodHandleStatics.*;

 /**

  * A symbolic reference obtained by cracking a direct method handle

  * into its consitutent symbolic parts.

  * To crack a direct method handle, call {@link Lookup#revealDirect Lookup.revealDirect}.

  * <h1><a name="directmh"></a>Direct Method Handles</h1>

  * A <em>direct method handle</em> represents a method, constructor, or field without

  * any intervening argument bindings or other transformations.

  * The method, constructor, or field referred to by a direct method handle is called

  * its <em>underlying member</em>.

  * Direct method handles may be obtained in any of these ways:

  * <ul>

  * <li>By executing an {@code ldc} instruction on a {@code CONSTANT_MethodHandle} constant.

  *     (See the Java Virtual Machine Specification, sections 4.4.8 and 5.4.3.)

  * <li>By calling one of the <a href="MethodHandles.Lookup.html#lookups">Lookup Factory Methods</a>,

  *     such as {@link Lookup#findVirtual Lookup.findVirtual},

  *     to resolve a symbolic reference into a method handle.

  *     A symbolic reference consists of a class, name string, and type.

  * <li>By calling the factory method {@link Lookup#unreflect Lookup.unreflect}

  *     or {@link Lookup#unreflectSpecial Lookup.unreflectSpecial}

  *     to convert a {@link Method} into a method handle.

  * <li>By calling the factory method {@link Lookup#unreflectConstructor Lookup.unreflectConstructor}

  *     to convert a {@link Constructor} into a method handle.

  * <li>By calling the factory method {@link Lookup#unreflectGetter Lookup.unreflectGetter}

  *     or {@link Lookup#unreflectSetter Lookup.unreflectSetter}

  *     to convert a {@link Field} into a method handle.

  * </ul>

  *

  * <h1>Restrictions on Cracking</h1>

  * Given a suitable {@code Lookup} object, it is possible to crack any direct method handle

  * to recover a symbolic reference for the underlying method, constructor, or field.

  * Cracking must be done via a {@code Lookup} object equivalent to that which created

  * the target method handle, or which has enough access permissions to recreate

  * an equivalent method handle.

  * <p>

  * If the underlying method is <a href="MethodHandles.Lookup.html#callsens">caller sensitive</a>,

  * the direct method handle will have been "bound" to a particular caller class, the

  * {@linkplain java.lang.invoke.MethodHandles.Lookup#lookupClass() lookup class}

  * of the lookup object used to create it.

  * Cracking this method handle with a different lookup class will fail

  * even if the underlying method is public (like {@code Class.forName}).

  * <p>

  * The requirement of lookup object matching provides a "fast fail" behavior

  * for programs which may otherwise trust erroneous revelation of a method

  * handle with symbolic information (or caller binding) from an unexpected scope.

  * Use {@link java.lang.invoke.MethodHandles#reflectAs} to override this limitation.

  *

  * <h1><a name="refkinds"></a>Reference kinds</h1>

  * The <a href="MethodHandles.Lookup.html#lookups">Lookup Factory Methods</a>

  * correspond to all major use cases for methods, constructors, and fields.

  * These use cases may be distinguished using small integers as follows:

  * <table border=1 cellpadding=5 summary="reference kinds">

  * <tr><th>reference kind</th><th>descriptive name</th><th>scope</th><th>member</th><th>behavior</th></tr>

  * <tr>

  *     <td>{@code 1}</td><td>{@code REF_getField}</td><td>{@code class}</td>

  *     <td>{@code FT f;}</td><td>{@code (T) this.f;}</td>

  * </tr>

  * <tr>

  *     <td>{@code 2}</td><td>{@code REF_getStatic}</td><td>{@code class} or {@code interface}</td>

  *     <td>{@code static}<br>{@code FT f;}</td><td>{@code (T) C.f;}</td>

  * </tr>

  * <tr>

  *     <td>{@code 3}</td><td>{@code REF_putField}</td><td>{@code class}</td>

  *     <td>{@code FT f;}</td><td>{@code this.f = x;}</td>

  * </tr>

  * <tr>

  *     <td>{@code 4}</td><td>{@code REF_putStatic}</td><td>{@code class}</td>

  *     <td>{@code static}<br>{@code FT f;}</td><td>{@code C.f = arg;}</td>

  * </tr>

  * <tr>

  *     <td>{@code 5}</td><td>{@code REF_invokeVirtual}</td><td>{@code class}</td>

  *     <td>{@code T m(A*);}</td><td>{@code (T) this.m(arg*);}</td>

  * </tr>

  * <tr>

  *     <td>{@code 6}</td><td>{@code REF_invokeStatic}</td><td>{@code class} or {@code interface}</td>

  *     <td>{@code static}<br>{@code T m(A*);}</td><td>{@code (T) C.m(arg*);}</td>

  * </tr>

  * <tr>

  *     <td>{@code 7}</td><td>{@code REF_invokeSpecial}</td><td>{@code class} or {@code interface}</td>

  *     <td>{@code T m(A*);}</td><td>{@code (T) super.m(arg*);}</td>

  * </tr>

  * <tr>

  *     <td>{@code 8}</td><td>{@code REF_newInvokeSpecial}</td><td>{@code class}</td>

  *     <td>{@code C(A*);}</td><td>{@code new C(arg*);}</td>

  * </tr>

  * <tr>

  *     <td>{@code 9}</td><td>{@code REF_invokeInterface}</td><td>{@code interface}</td>

  *     <td>{@code T m(A*);}</td><td>{@code (T) this.m(arg*);}</td>

  * </tr>

  * </table>

  * @since 1.8

  */

 public

 interface MethodHandleInfo {

     /**

      * A direct method handle reference kind,

      * as defined in the <a href="MethodHandleInfo.html#refkinds">table above</a>.

      */

     public static final int

         REF_getField                = Constants.REF_getField,

         REF_getStatic               = Constants.REF_getStatic,

         REF_putField                = Constants.REF_putField,

         REF_putStatic               = Constants.REF_putStatic,

         REF_invokeVirtual           = Constants.REF_invokeVirtual,

         REF_invokeStatic            = Constants.REF_invokeStatic,

         REF_invokeSpecial           = Constants.REF_invokeSpecial,

         REF_newInvokeSpecial        = Constants.REF_newInvokeSpecial,

         REF_invokeInterface         = Constants.REF_invokeInterface;

     /**

      * Returns the reference kind of the cracked method handle, which in turn

      * determines whether the method handle's underlying member was a constructor, method, or field.

      * See the <a href="MethodHandleInfo.html#refkinds">table above</a> for definitions.

      * @return the integer code for the kind of reference used to access the underlying member

      */

     public int getReferenceKind();

     /**

      * Returns the class in which the cracked method handle's underlying member was defined.

      * @return the declaring class of the underlying member

      */

     public Class<?> getDeclaringClass();

     /**

      * Returns the name of the cracked method handle's underlying member.

      * This is {@code "<init>"} if the underlying member was a constructor,

      * else it is a simple method name or field name.

      * @return the simple name of the underlying member

      */

     public String getName();

     /**

      * Returns the nominal type of the cracked symbolic reference, expressed as a method type.

      * If the reference is to a constructor, the return type will be {@code void}.

      * If it is to a non-static method, the method type will not mention the {@code this} parameter.

      * If it is to a field and the requested access is to read the field,

      * the method type will have no parameters and return the field type.

      * If it is to a field and the requested access is to write the field,

      * the method type will have one parameter of the field type and return {@code void}.

      * <p>

      * Note that original direct method handle may include a leading {@code this} parameter,

      * or (in the case of a constructor) will replace the {@code void} return type

      * with the constructed class.

      * The nominal type does not include any {@code this} parameter,

      * and (in the case of a constructor) will return {@code void}.

      * @return the type of the underlying member, expressed as a method type

      */

     public MethodType getMethodType();

     // Utility methods.

     // NOTE: class/name/type and reference kind constitute a symbolic reference

     // member and modifiers are an add-on, derived from Core Reflection (or the equivalent)

     /**

      * Reflects the underlying member as a method, constructor, or field object.

      * If the underlying member is public, it is reflected as if by

      * {@code getMethod}, {@code getConstructor}, or {@code getField}.

      * Otherwise, it is reflected as if by

      * {@code getDeclaredMethod}, {@code getDeclaredConstructor}, or {@code getDeclaredField}.

      * The underlying member must be accessible to the given lookup object.

      * @param <T> the desired type of the result, either {@link Member} or a subtype

      * @param expected a class object representing the desired result type {@code T}

      * @param lookup the lookup object that created this MethodHandleInfo, or one with equivalent access privileges

      * @return a reference to the method, constructor, or field object

      * @exception ClassCastException if the member is not of the expected type

      * @exception NullPointerException if either argument is {@code null}

      * @exception IllegalArgumentException if the underlying member is not accessible to the given lookup object

      */

     public <T extends Member> T reflectAs(Class<T> expected, Lookup lookup);

     /**

      * Returns the access modifiers of the underlying member.

      * @return the Java language modifiers for underlying member,

      *         or -1 if the member cannot be accessed

      * @see Modifier

      * @see #reflectAs

      */

     public int getModifiers();

     /**

      * Determines if the underlying member was a variable arity method or constructor.

      * Such members are represented by method handles that are varargs collectors.

      * @implSpec

      * This produces a result equivalent to:

      * <pre>{@code

      *     getReferenceKind() >= REF_invokeVirtual && Modifier.isTransient(getModifiers())

      * }</pre>

      *

      *

      * @return {@code true} if and only if the underlying member was declared with variable arity.

      */

     // spelling derived from java.lang.reflect.Executable, not MethodHandle.isVarargsCollector

     public default boolean isVarArgs()  {

         // fields are never varargs:

         if (MethodHandleNatives.refKindIsField((byte) getReferenceKind()))

             return false;

         // not in the public API: Modifier.VARARGS

         final int ACC_VARARGS = 0x00000080;  // from JVMS 4.6 (Table 4.20)

         assert(ACC_VARARGS == Modifier.TRANSIENT);

         return Modifier.isTransient(getModifiers());

     }

     /**

      * Returns the descriptive name of the given reference kind,

      * as defined in the <a href="MethodHandleInfo.html#refkinds">table above</a>.

      * The conventional prefix "REF_" is omitted.

      * @param referenceKind an integer code for a kind of reference used to access a class member

      * @return a mixed-case string such as {@code "getField"}

      * @exception IllegalArgumentException if the argument is not a valid

      *            <a href="MethodHandleInfo.html#refkinds">reference kind number</a>

      */

     public static String referenceKindToString(int referenceKind) {

         if (!MethodHandleNatives.refKindIsValid(referenceKind))

             throw newIllegalArgumentException("invalid reference kind", referenceKind);

         return MethodHandleNatives.refKindName((byte)referenceKind);

     }

     /**

      * Returns a string representation for a {@code MethodHandleInfo},

      * given the four parts of its symbolic reference.

      * This is defined to be of the form {@code "RK C.N:MT"}, where {@code RK} is the

      * {@linkplain #referenceKindToString reference kind string} for {@code kind},

      * {@code C} is the {@linkplain java.lang.Class#getName name} of {@code defc}

      * {@code N} is the {@code name}, and

      * {@code MT} is the {@code type}.

      * These four values may be obtained from the

      * {@linkplain #getReferenceKind reference kind},

      * {@linkplain #getDeclaringClass declaring class},

      * {@linkplain #getName member name},

      * and {@linkplain #getMethodType method type}

      * of a {@code MethodHandleInfo} object.

      *

      * @implSpec

      * This produces a result equivalent to:

      * <pre>{@code

      *     String.format("%s %s.%s:%s", referenceKindToString(kind), defc.getName(), name, type)

      * }</pre>

      *

      * @param kind the {@linkplain #getReferenceKind reference kind} part of the symbolic reference

      * @param defc the {@linkplain #getDeclaringClass declaring class} part of the symbolic reference

      * @param name the {@linkplain #getName member name} part of the symbolic reference

      * @param type the {@linkplain #getMethodType method type} part of the symbolic reference

      * @return a string of the form {@code "RK C.N:MT"}

      * @exception IllegalArgumentException if the first argument is not a valid

      *            <a href="MethodHandleInfo.html#refkinds">reference kind number</a>

      * @exception NullPointerException if any reference argument is {@code null}

      */

     public static String toString(int kind, Class<?> defc, String name, MethodType type) {

         Objects.requireNonNull(name); Objects.requireNonNull(type);

         return String.format("%s %s.%s:%s", referenceKindToString(kind), defc.getName(), name, type);

     }

 }