com.landawn.abacus.util.LazyInitializer Maven / Gradle / Ivy

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A general programming library in Java/Android. It's easy to learn and simple to use with concise and powerful APIs.

There is a newer version: 5.3.16

/*
 * Copyright (c) 2019, Haiyang Li.
 *
 * 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.landawn.abacus.util;

import com.landawn.abacus.util.function.Supplier;

public final class LazyInitializer implements Supplier {
    private volatile boolean initialized = false;
    private volatile T value = null;
    private final Supplier supplier;

    LazyInitializer(final Supplier supplier) {
        N.checkArgNotNull(supplier, "supplier");

        this.supplier = supplier;
    }

    @Override
    public T get() {
        if (!initialized) {
            synchronized (this) {
                if (!initialized) {
                    value = supplier.get();

                    initialized = true;
                }

            }
        }

        return value;
    }

    /**
     *
     * @param 
     * @param supplier
     * @return
     */
    public static  LazyInitializer of(final Supplier supplier) {
        N.checkArgNotNull(supplier);

        if (supplier instanceof LazyInitializer) {
            return (LazyInitializer) supplier;
        }

        return new LazyInitializer<>(supplier);
    }
}