/*
 * Copyright 2015 Michael Rozumyanskiy
 *
 * 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 io.michaelrocks.lightsaber;

import javax.inject.Provider;

public class LazyAdapter<T> implements Lazy<T> {
    private final Provider<T> provider;
    private volatile T instance;
    private final Object instanceLock = new Object();

    public LazyAdapter(final Provider<T> provider) {
        this.provider = provider;
    }

    @Override
    public T get() {
        if (instance == null) {
            synchronized (instanceLock) {
                if (instance == null) {
                    instance = provider.get();
                }
            }
        }
        return instance;
    }
}

Implement a lazy adapter for a provider