Java基础

合并数组为String并插入分隔符

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StringUtils.join(Arrarys.asList(T... a),"-");

List过大时拆批处理(guava包)

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Lists.partition(List<T> list, int size).forEach(subList->doMethod(subList));

通过Stream List转List

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List<Integer> list = otherList.stream().map(subInt->{
    return new Integer(1);
}).collect(Collectors.toList());

近端缓存（guava包）

示例如下：

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@Component
public class LocalCacheHelper {

    @Value("${localCache.expireTime:60}")
    private Integer expireTime;

    @Value("${localCache.maxSize:2000}")
    private Integer maxSize;

    private static Cache<String, String> cache;


    @PostConstruct
    private void init() {

        //创建一个LoadingCache，并可以进行一些简单的缓存配置
        cache = CacheBuilder.newBuilder()
            //最大容量为100（基于容量进行回收）
            .maximumSize(maxSize)
            //配置写入后多久使缓存过期
            .expireAfterWrite(expireTime, TimeUnit.MINUTES)
            .recordStats()
            .build();
    }

    public static <T>String get(String key, Supplier<T> supplier,UmsLogger logger) {
        try {
            logger.build("key", key);
            return cache.get(key, () -> {
                logger.info("do not use cache");
                return JSON.toJSONString(supplier.get());
            });
        } catch (ExecutionException e) {
            logger.error(e.getMessage());
        }
        return null;
    }

    public static void put(String key, Object value) {
        String v = JSON.toJSONString(value);
        cache.put(key, v);
    }
 }

POJO转换工具类

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/**
 * pojo转换工具类
 *
 * @author lich.wangy
 * @date 2018-11-08
 */
public class ModelConvertUtils {

    /**
     * 把source对象的属性复制到result对象中
     *
     * 例如将A a 转为B b
     * B b = PojoConvertUtils.convert(a,B.class);
     *
     * @param source
     * @param s
     * @param <R>
     * @param <S>
     * @return
     * @throws IllegalAccessException
     * @throws InstantiationException
     */
    public static <R, S> R convert(S source, Supplier<R> s) {
        if (source == null) {
            return null;
        }
        R result = s.get();
        BeanUtils.copyProperties(source, result);
        return result;

    }

    /**
     * 把source对象列表复制到result对象列表
     * * 例如将List<A> a 转为List<B> b
     * List<B> b = PojoConvertUtils.convert(a,B.class);
     *
     * @param sourceList
     * @param supplier
     * @param <R>
     * @param <S>
     * @return
     * @throws IllegalAccessException
     * @throws InstantiationException
     */
    public static <R, S> List<R> convert(List<S> sourceList, Supplier<R> supplier) {
        if (sourceList == null) {
            return null;
        }
        return sourceList.stream().map(each -> convert(each, supplier)).collect(Collectors.toList());
    }


}