Present.java

package com.zhuinden.simplestackdemoexamplefragments.util.optional;
/*
 * 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.
 */

import android.support.annotation.Nullable;

import com.zhuinden.simplestackdemoexamplefragments.util.Preconditions;

import java.util.Collections;
import java.util.Set;

/**
 * Implementation of an {@link Optional} containing a reference.
 */
final class Present<T>
        extends Optional<T> {
    private final T reference;

    Present(T reference) {
        this.reference = reference;
    }

    @Override
    public boolean isPresent() {
        return true;
    }

    @Override
    public T get() {
        return reference;
    }

    @Override
    public T or(T defaultValue) {
        Preconditions.checkNotNull(defaultValue, "use Optional.orNull() instead of Optional.or(null)");
        return reference;
    }

    @Override
    public Optional<T> or(Optional<? extends T> secondChoice) {
        Preconditions.checkNotNull(secondChoice);
        return this;
    }

    @Override
    public T orNull() {
        return reference;
    }

    @Override
    public Set<T> asSet() {
        return Collections.singleton(reference);
    }

    @Override
    public boolean equals(@Nullable Object object) {
        if(object instanceof Present) {
            Present<?> other = (Present<?>) object;
            return reference.equals(other.reference);
        }
        return false;
    }

    @Override
    public int hashCode() {
        return 0x598df91c + reference.hashCode();
    }

    @Override
    public String toString() {
        return "Optional.of(" + reference + ")";
    }

    private static final long serialVersionUID = 0;
}