com.google.common.reflect.TypeParameter.java Source code

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Here is the source code for com.google.common.reflect.TypeParameter.java

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/*
 * Copyright (C) 2011 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.common.reflect;

import static com.google.common.base.Preconditions.checkArgument;

import com.google.common.annotations.Beta;

import java.lang.reflect.Type;
import java.lang.reflect.TypeVariable;

import javax.annotation.Nullable;

/**
 * Captures a free type variable that can be used in {@link TypeToken#where}.
 * For example:
 *
 * <pre>   {@code
 *   static <T> TypeToken<List<T>> listOf(Class<T> elementType) {
 *     return new TypeToken<List<T>>() {}
 *         .where(new TypeParameter<T>() {}, elementType);
 *   }}</pre>
 *
 * @author Ben Yu
 * @since 12.0
 */
@Beta
public abstract class TypeParameter<T> extends TypeCapture<T> {

    final TypeVariable<?> typeVariable;

    protected TypeParameter() {
        Type type = capture();
        checkArgument(type instanceof TypeVariable, "%s should be a type variable.", type);
        this.typeVariable = (TypeVariable<?>) type;
    }

    @Override
    public final int hashCode() {
        return typeVariable.hashCode();
    }

    @Override
    public final boolean equals(@Nullable Object o) {
        if (o instanceof TypeParameter) {
            TypeParameter<?> that = (TypeParameter<?>) o;
            return typeVariable.equals(that.typeVariable);
        }
        return false;
    }

    @Override
    public String toString() {
        return typeVariable.toString();
    }
}