记录-java-jdk8+提供部分工具类

1.java.util.stream.Collectors

public ResponsePreview post(String url, Map<String,String> headers, Map<String,String> paras){
        HttpPost request = createHttpPost(url, headers);
        EntityBuilder entityBuilder = EntityBuilder.create();
        Set<Entry<String, String>> entrySet = paras.entrySet();

//set替换为list并转换集合里的实体对象，entry = new BasicNameValuePair(entry.getKey(), entry.getValue())  再收集(collect)起来,使用Collectors.toList()收集放到pairs List里

　　　　List<NameValuePair> pairs = entrySet.parallelStream() .map(entry -> new BasicNameValuePair(entry.getKey(), entry.getValue())).collect(Collectors.toList()); 

//
//        List<NameValuePair> pairs = new ArrayList<>();
//        for (Entry<String, String> entry : entrySet) {
//            BasicNameValuePair pair = new BasicNameValuePair(entry.getKey(), entry.getValue());
//            pairs.add(pair);
//        }
        entityBuilder.setParameters(pairs);
        request.setEntity(entityBuilder.build());
        return execute(request);
    }

2.java.util.function.Function  目前略懂。

package java.util.function;

import java.util.Objects;

/**
 * Represents a function that accepts one argument and produces a result.
 *
 * <p>This is a <a href="package-summary.html">functional interface</a>
 * whose functional method is {@link #apply(Object)}.
 *
 * @param <T> the type of the input to the function
 * @param <R> the type of the result of the function
 *
 * @since 1.8
 */
@FunctionalInterface
public interface Function<T, R> {

    /**
     * Applies this function to the given argument.
     *
     * @param t the function argument
     * @return the function result
     */
    R apply(T t);

    /**
     * Returns a composed function that first applies the {@code before}
     * function to its input, and then applies this function to the result.
     * If evaluation of either function throws an exception, it is relayed to
     * the caller of the composed function.
     *
     * @param <V> the type of input to the {@code before} function, and to the
     *           composed function
     * @param before the function to apply before this function is applied
     * @return a composed function that first applies the {@code before}
     * function and then applies this function
     * @throws NullPointerException if before is null
     *
     * @see #andThen(Function)
     */
    default <V> Function<V, R> compose(Function<? super V, ? extends T> before) {
        Objects.requireNonNull(before);
        return (V v) -> apply(before.apply(v));
    }

    /**
     * Returns a composed function that first applies this function to
     * its input, and then applies the {@code after} function to the result.
     * If evaluation of either function throws an exception, it is relayed to
     * the caller of the composed function.
     *
     * @param <V> the type of output of the {@code after} function, and of the
     *           composed function
     * @param after the function to apply after this function is applied
     * @return a composed function that first applies this function and then
     * applies the {@code after} function
     * @throws NullPointerException if after is null
     *
     * @see #compose(Function)
     */
    default <V> Function<T, V> andThen(Function<? super R, ? extends V> after) {
        Objects.requireNonNull(after);
        return (T t) -> after.apply(apply(t));
    }

    /**
     * Returns a function that always returns its input argument.
     *
     * @param <T> the type of the input and output objects to the function
     * @return a function that always returns its input argument
     */
    static <T> Function<T, T> identity() {
        return t -> t;
    }
}