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A simple Java Pool

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package com.github.phantomthief.pool.impl;

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

import java.util.function.Supplier;

import javax.annotation.CheckReturnValue;
import javax.annotation.Nonnegative;
import javax.annotation.Nonnull;
import javax.annotation.concurrent.NotThreadSafe;

import com.github.phantomthief.pool.KeyAffinity;
import com.github.phantomthief.util.ThrowableConsumer;

/**
 * @author w.vela
 * Created on 2018-02-09.
 */
@NotThreadSafe
public class KeyAffinityBuilder {

    private static final int RANDOM_THRESHOLD = 20;

    private Supplier factory;
    private int count;
    private ThrowableConsumer depose;
    private Boolean usingRandom;

    public  KeyAffinity build() {
        ensure();
        return new LazyKeyAffinity<>(this::buildInner);
    }

     KeyAffinity buildInner() {
        return new KeyAffinityImpl<>(factory, count, depose, usingRandom);
    }

    void ensure() {
        if (count <= 0) {
            throw new IllegalArgumentException("no count found.");
        }
        if (depose == null) {
            depose = it -> {};
        }
        if (usingRandom == null) {
            usingRandom = count > RANDOM_THRESHOLD;
        }
    }

    @SuppressWarnings("unchecked")
    @CheckReturnValue
    public > T factory(@Nonnull Supplier factory) {
        this.factory = checkNotNull(factory);
        return (T) this;
    }

    /**
     * whether to use random strategy or less concurrency strategy
     * @param value {@code true} is random strategy and {@code false} is less concurrency strategy
     * default value is {@code true} is {@link #count} larger than {@link #RANDOM_THRESHOLD}
     */
    @SuppressWarnings("unchecked")
    @CheckReturnValue
    public > T usingRandom(boolean value) {
        this.usingRandom = value;
        return (T) this;
    }

    @SuppressWarnings("unchecked")
    @CheckReturnValue
    public > T count(@Nonnegative int count) {
        checkArgument(count > 0);
        this.count = count;
        return (T) this;
    }

    @SuppressWarnings("unchecked")
    @CheckReturnValue
    public > T
            depose(@Nonnegative ThrowableConsumer depose) {
        this.depose = checkNotNull(depose);
        return (T) this;
    }
}