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package spring.turbo.bean;

import org.springframework.lang.Nullable;
import spring.turbo.lang.Singleton;
import spring.turbo.util.StringPool;

import java.io.Serializable;
import java.util.Optional;

/**
 * 空值占位对象
 *
 * @author 应卓
 * @see #getInstance()
 * @since 1.0.0
 */
@Singleton
public final class Null implements Serializable {

    /**
     * 私有构造方法
     */
    private Null() {
        super();
    }

    public static Null getInstance() {
        return AsyncAvoid.INSTANCE;
    }

    public static Object replaceIfNull(@Nullable Object obj) {
        return Optional.ofNullable(obj).orElse(getInstance());
    }

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

    // -----------------------------------------------------------------------------------------------------------------

    // 延迟加载
    private static class AsyncAvoid {
        private static final Null INSTANCE = new Null();
    }

}