import java.lang.invoke.LambdaForm.BasicType; //导入依赖的package包/类
static
MethodHandle filterArgument(MethodHandle target, int pos, MethodHandle filter) {
    filterArgumentChecks(target, pos, filter);
    MethodType targetType = target.type();
    MethodType filterType = filter.type();
    BoundMethodHandle result = target.rebind();
    Class<?> newParamType = filterType.parameterType(0);
    LambdaForm lform = result.editor().filterArgumentForm(1 + pos, BasicType.basicType(newParamType));
    MethodType newType = targetType.changeParameterType(pos, newParamType);
    result = result.copyWithExtendL(newType, lform, filter);
    return result;
}
 

import java.lang.invoke.LambdaForm.BasicType; //导入依赖的package包/类
private static
MethodHandle dropArguments0(MethodHandle target, int pos, List<Class<?>> valueTypes) {
    MethodType oldType = target.type();  // get NPE
    int dropped = dropArgumentChecks(oldType, pos, valueTypes);
    MethodType newType = oldType.insertParameterTypes(pos, valueTypes);
    if (dropped == 0)  return target;
    BoundMethodHandle result = target.rebind();
    LambdaForm lform = result.form;
    int insertFormArg = 1 + pos;
    for (Class<?> ptype : valueTypes) {
        lform = lform.editor().addArgumentForm(insertFormArg++, BasicType.basicType(ptype));
    }
    result = result.copyWith(newType, lform);
    return result;
}
 

import java.lang.invoke.LambdaForm.BasicType; //导入依赖的package包/类
private static MethodHandle makeIdentity(Class<?> ptype) {
    MethodType mtype = MethodType.methodType(ptype, ptype);
    LambdaForm lform = LambdaForm.identityForm(BasicType.basicType(ptype));
    return MethodHandleImpl.makeIntrinsic(mtype, lform, Intrinsic.IDENTITY);
}
 

import java.lang.invoke.LambdaForm.BasicType; //导入依赖的package包/类
private static MethodHandle makeZero(Class<?> rtype) {
    MethodType mtype = MethodType.methodType(rtype);
    LambdaForm lform = LambdaForm.zeroForm(BasicType.basicType(rtype));
    return MethodHandleImpl.makeIntrinsic(mtype, lform, Intrinsic.ZERO);
}
 

import java.lang.invoke.LambdaForm.BasicType; //导入依赖的package包/类
/**
     * Produces a method handle which will discard some dummy arguments
     * before calling some other specified <i>target</i> method handle.
     * The type of the new method handle will be the same as the target's type,
     * except it will also include the dummy argument types,
     * at some given position.
     * <p>
     * The {@code pos} argument may range between zero and <i>N</i>,
     * where <i>N</i> is the arity of the target.
     * If {@code pos} is zero, the dummy arguments will precede
     * the target's real arguments; if {@code pos} is <i>N</i>
     * they will come after.
     * <p>
     * <b>Example:</b>
     * <blockquote><pre>{@code
import static java.lang.invoke.MethodHandles.*;
import static java.lang.invoke.MethodType.*;
...
MethodHandle cat = lookup().findVirtual(String.class,
  "concat", methodType(String.class, String.class));
assertEquals("xy", (String) cat.invokeExact("x", "y"));
MethodType bigType = cat.type().insertParameterTypes(0, int.class, String.class);
MethodHandle d0 = dropArguments(cat, 0, bigType.parameterList().subList(0,2));
assertEquals(bigType, d0.type());
assertEquals("yz", (String) d0.invokeExact(123, "x", "y", "z"));
     * }</pre></blockquote>
     * <p>
     * This method is also equivalent to the following code:
     * <blockquote><pre>
     * {@link #dropArguments(MethodHandle,int,Class...) dropArguments}{@code (target, pos, valueTypes.toArray(new Class[0]))}
     * </pre></blockquote>
     * @param target the method handle to invoke after the arguments are dropped
     * @param valueTypes the type(s) of the argument(s) to drop
     * @param pos position of first argument to drop (zero for the leftmost)
     * @return a method handle which drops arguments of the given types,
     *         before calling the original method handle
     * @throws NullPointerException if the target is null,
     *                              or if the {@code valueTypes} list or any of its elements is null
     * @throws IllegalArgumentException if any element of {@code valueTypes} is {@code void.class},
     *                  or if {@code pos} is negative or greater than the arity of the target,
     *                  or if the new method handle's type would have too many parameters
     */
    public static
    MethodHandle dropArguments(MethodHandle target, int pos, List<Class<?>> valueTypes) {
        MethodType oldType = target.type();  // get NPE
        int dropped = dropArgumentChecks(oldType, pos, valueTypes);
        MethodType newType = oldType.insertParameterTypes(pos, valueTypes);
        if (dropped == 0)  return target;
        BoundMethodHandle result = target.rebind();
        LambdaForm lform = result.form;
        int insertFormArg = 1 + pos;
        for (Class<?> ptype : valueTypes) {
            lform = lform.editor().addArgumentForm(insertFormArg++, BasicType.basicType(ptype));
        }
        result = result.copyWith(newType, lform);
        return result;
    }
 

import java.lang.invoke.LambdaForm.BasicType; //导入依赖的package包/类
/**
     * Produces a method handle which will discard some dummy arguments
     * before calling some other specified <i>target</i> method handle.
     * The type of the new method handle will be the same as the target's type,
     * except it will also include the dummy argument types,
     * at some given position.
     * <p>
     * The {@code pos} argument may range between zero and <i>N</i>,
     * where <i>N</i> is the arity of the target.
     * If {@code pos} is zero, the dummy arguments will precede
     * the target's real arguments; if {@code pos} is <i>N</i>
     * they will come after.
     * <p>
     * <b>Example:</b>
     * <blockquote><pre>{@code
import static java.lang.invoke.MethodHandles.*;
import static java.lang.invoke.MethodType.*;
...
MethodHandle cat = lookup().findVirtual(String.class,
  "concat", methodType(String.class, String.class));
assertEquals("xy", (String) cat.invokeExact("x", "y"));
MethodType bigType = cat.type().insertParameterTypes(0, int.class, String.class);
MethodHandle d0 = dropArguments(cat, 0, bigType.parameterList().subList(0,2));
assertEquals(bigType, d0.type());
assertEquals("yz", (String) d0.invokeExact(123, "x", "y", "z"));
     * }</pre></blockquote>
     * <p>
     * This method is also equivalent to the following code:
     * <blockquote><pre>
     * {@link #dropArguments(MethodHandle,int,Class...) dropArguments}{@code (target, pos, valueTypes.toArray(new Class[0]))}
     * </pre></blockquote>
     * @param target the method handle to invoke after the arguments are dropped
     * @param valueTypes the type(s) of the argument(s) to drop
     * @param pos position of first argument to drop (zero for the leftmost)
     * @return a method handle which drops arguments of the given types,
     *         before calling the original method handle
     * @throws NullPointerException if the target is null,
     *                              or if the {@code valueTypes} list or any of its elements is null
     * @throws IllegalArgumentException if any element of {@code valueTypes} is {@code void.class},
     *                  or if {@code pos} is negative or greater than the arity of the target,
     *                  or if the new method handle's type would have too many parameters
     */
    public static
    MethodHandle dropArguments(MethodHandle target, int pos, List<Class<?>> valueTypes) {
        valueTypes = copyTypes(valueTypes);
        MethodType oldType = target.type();  // get NPE
        int dropped = dropArgumentChecks(oldType, pos, valueTypes);
        MethodType newType = oldType.insertParameterTypes(pos, valueTypes);
        if (dropped == 0)  return target;
        BoundMethodHandle result = target.rebind();
        LambdaForm lform = result.form;
        int insertFormArg = 1 + pos;
        for (Class<?> ptype : valueTypes) {
            lform = lform.editor().addArgumentForm(insertFormArg++, BasicType.basicType(ptype));
        }
        result = result.copyWith(newType, lform);
        return result;
    }
 

import java.lang.invoke.LambdaForm.BasicType; //导入依赖的package包/类
private static MethodHandle makeIdentity(Class<?> ptype) {
    MethodType mtype = methodType(ptype, ptype);
    LambdaForm lform = LambdaForm.identityForm(BasicType.basicType(ptype));
    return MethodHandleImpl.makeIntrinsic(mtype, lform, Intrinsic.IDENTITY);
}
 

import java.lang.invoke.LambdaForm.BasicType; //导入依赖的package包/类
private static MethodHandle makeZero(Class<?> rtype) {
    MethodType mtype = methodType(rtype);
    LambdaForm lform = LambdaForm.zeroForm(BasicType.basicType(rtype));
    return MethodHandleImpl.makeIntrinsic(mtype, lform, Intrinsic.ZERO);
}
 

import java.lang.invoke.LambdaForm.BasicType; //导入依赖的package包/类
/**
     * Adapts a target method handle by post-processing
     * its return value (if any) with a filter (another method handle).
     * The result of the filter is returned from the adapter.
     * <p>
     * If the target returns a value, the filter must accept that value as
     * its only argument.
     * If the target returns void, the filter must accept no arguments.
     * <p>
     * The return type of the filter
     * replaces the return type of the target
     * in the resulting adapted method handle.
     * The argument type of the filter (if any) must be identical to the
     * return type of the target.
     * <p><b>Example:</b>
     * <blockquote><pre>{@code
import static java.lang.invoke.MethodHandles.*;
import static java.lang.invoke.MethodType.*;
...
MethodHandle cat = lookup().findVirtual(String.class,
  "concat", methodType(String.class, String.class));
MethodHandle length = lookup().findVirtual(String.class,
  "length", methodType(int.class));
System.out.println((String) cat.invokeExact("x", "y")); // xy
MethodHandle f0 = filterReturnValue(cat, length);
System.out.println((int) f0.invokeExact("x", "y")); // 2
     * }</pre></blockquote>
     * <p>Here is pseudocode for the resulting adapter. In the code,
     * {@code T}/{@code t} represent the result type and value of the
     * {@code target}; {@code V}, the result type of the {@code filter}; and
     * {@code A}/{@code a}, the types and values of the parameters and arguments
     * of the {@code target} as well as the resulting adapter.
     * <blockquote><pre>{@code
     * T target(A...);
     * V filter(T);
     * V adapter(A... a) {
     *   T t = target(a...);
     *   return filter(t);
     * }
     * // and if the target has a void return:
     * void target2(A...);
     * V filter2();
     * V adapter2(A... a) {
     *   target2(a...);
     *   return filter2();
     * }
     * // and if the filter has a void return:
     * T target3(A...);
     * void filter3(V);
     * void adapter3(A... a) {
     *   T t = target3(a...);
     *   filter3(t);
     * }
     * }</pre></blockquote>
     * <p>
     * <em>Note:</em> The resulting adapter is never a {@linkplain MethodHandle#asVarargsCollector
     * variable-arity method handle}, even if the original target method handle was.
     * @param target the method handle to invoke before filtering the return value
     * @param filter method handle to call on the return value
     * @return method handle which incorporates the specified return value filtering logic
     * @throws NullPointerException if either argument is null
     * @throws IllegalArgumentException if the argument list of {@code filter}
     *          does not match the return type of target as described above
     */
    public static
    MethodHandle filterReturnValue(MethodHandle target, MethodHandle filter) {
        MethodType targetType = target.type();
        MethodType filterType = filter.type();
        filterReturnValueChecks(targetType, filterType);
        BoundMethodHandle result = target.rebind();
        BasicType rtype = BasicType.basicType(filterType.returnType());
        LambdaForm lform = result.editor().filterReturnForm(rtype, false);
        MethodType newType = targetType.changeReturnType(filterType.returnType());
        result = result.copyWithExtendL(newType, lform, filter);
        return result;
    }