001/*
002 * Copyright (C) 2012 The Guava Authors
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
005 * in compliance with the License. You may obtain a copy of the License at
006 *
007 * http://www.apache.org/licenses/LICENSE-2.0
008 *
009 * Unless required by applicable law or agreed to in writing, software distributed under the License
010 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
011 * or implied. See the License for the specific language governing permissions and limitations under
012 * the License.
013 */
014
015package com.google.common.reflect;
016
017import static com.google.common.base.Preconditions.checkNotNull;
018
019import com.google.common.annotations.Beta;
020import com.google.common.collect.FluentIterable;
021import com.google.common.collect.ImmutableList;
022import java.lang.annotation.Annotation;
023import java.lang.reflect.AnnotatedElement;
024import javax.annotation.CheckForNull;
025import org.checkerframework.checker.nullness.qual.Nullable;
026
027/**
028 * Represents a method or constructor parameter.
029 *
030 * <p><b>Note:</b> Since Java 8 introduced {@link java.lang.reflect.Parameter} to represent method
031 * and constructor parameters, this class is no longer necessary. We intend to deprecate it in a
032 * future version.
033 *
034 * @author Ben Yu
035 * @since 14.0
036 */
037@Beta
038@ElementTypesAreNonnullByDefault
039public final class Parameter implements AnnotatedElement {
040
041  private final Invokable<?, ?> declaration;
042  private final int position;
043  private final TypeToken<?> type;
044  private final ImmutableList<Annotation> annotations;
045
046  Parameter(
047      Invokable<?, ?> declaration, int position, TypeToken<?> type, Annotation[] annotations) {
048    this.declaration = declaration;
049    this.position = position;
050    this.type = type;
051    this.annotations = ImmutableList.copyOf(annotations);
052  }
053
054  /** Returns the type of the parameter. */
055  public TypeToken<?> getType() {
056    return type;
057  }
058
059  /** Returns the {@link Invokable} that declares this parameter. */
060  public Invokable<?, ?> getDeclaringInvokable() {
061    return declaration;
062  }
063
064  @Override
065  public boolean isAnnotationPresent(Class<? extends Annotation> annotationType) {
066    return getAnnotation(annotationType) != null;
067  }
068
069  @Override
070  @CheckForNull
071  public <A extends Annotation> A getAnnotation(Class<A> annotationType) {
072    checkNotNull(annotationType);
073    for (Annotation annotation : annotations) {
074      if (annotationType.isInstance(annotation)) {
075        return annotationType.cast(annotation);
076      }
077    }
078    return null;
079  }
080
081  @Override
082  public Annotation[] getAnnotations() {
083    return getDeclaredAnnotations();
084  }
085
086  /** @since 18.0 */
087  // @Override on JDK8
088  public <A extends Annotation> A[] getAnnotationsByType(Class<A> annotationType) {
089    return getDeclaredAnnotationsByType(annotationType);
090  }
091
092  /** @since 18.0 */
093  // @Override on JDK8
094  @Override
095  public Annotation[] getDeclaredAnnotations() {
096    return annotations.toArray(new Annotation[0]);
097  }
098
099  /** @since 18.0 */
100  // @Override on JDK8
101  @CheckForNull
102  public <A extends Annotation> A getDeclaredAnnotation(Class<A> annotationType) {
103    checkNotNull(annotationType);
104    return FluentIterable.from(annotations).filter(annotationType).first().orNull();
105  }
106
107  /** @since 18.0 */
108  // @Override on JDK8
109  public <A extends Annotation> A[] getDeclaredAnnotationsByType(Class<A> annotationType) {
110    @Nullable
111    A[] result = FluentIterable.from(annotations).filter(annotationType).toArray(annotationType);
112    @SuppressWarnings("nullness") // safe because the input list contains no nulls
113    A[] cast = (A[]) result;
114    return cast;
115  }
116
117  @Override
118  public boolean equals(@CheckForNull Object obj) {
119    if (obj instanceof Parameter) {
120      Parameter that = (Parameter) obj;
121      return position == that.position && declaration.equals(that.declaration);
122    }
123    return false;
124  }
125
126  @Override
127  public int hashCode() {
128    return position;
129  }
130
131  @Override
132  public String toString() {
133    return type + " arg" + position;
134  }
135}