第十四届蓝桥杯c++研究生组

🔍目的

🔍解释

真实世界例子

通俗描述

维基百科

程序实例

创建一个由not ，or ，and ，contains方法组成的接口

// 用于查找文本中的行的功能界面。
public interface Finder {

	// 在文本中查找行的函数。
	List<String> find(String text);

	// 函数{@link #find(String)}的简单实现。
	static Finder contains(String word) {
    		return txt -> Stream.of(txt.split("\n"))
        		.filter(line -> line.toLowerCase().contains(word.toLowerCase()))
        		.collect(Collectors.toList());
  	}

	// 组合器：not。
	default Finder not(Finder notFinder) {
    		return txt -> {
      			List<String> res = this.find(txt);
      			res.removeAll(notFinder.find(txt));
      			return res;
    			};
  	}

	// 组合器：or。
	default Finder or(Finder orFinder) {
    		return txt -> {
      			List<String> res = this.find(txt);
      			res.addAll(orFinder.find(txt));
      			return res;
    			};
	}

	// 组合器：and。
	default Finder and(Finder andFinder) {
    		return
        	txt -> this
            		.find(txt)
            		.stream()
            		.flatMap(line -> andFinder.find(line).stream())
            		.collect(Collectors.toList());
  	}
	...
}

另一个组合器用于一些复杂的查找器advancedFinder, filteredFinder, specializedFinder和expandedFinder。 

// 由简单取景器组成的复杂取景器。
public class Finders {

	private Finders() {
  	}

	// Finder 用于查找复杂的查询。
	public static Finder advancedFinder(String query, String orQuery, String notQuery) {
    		return
        		Finder.contains(query)
            			.or(Finder.contains(orQuery))
            			.not(Finder.contains(notQuery));
	}

	// 过滤查找器也会查找包含排除查询的查询。
	public static Finder filteredFinder(String query, String... excludeQueries) {
		var finder = Finder.contains(query);

    		for (String q : excludeQueries) {
      			finder = finder.not(Finder.contains(q));
    		}
    		return finder;
	}

	// 专门查询。 每个下一个查询都会在上一个结果中查找。
	public static Finder specializedFinder(String... queries) {
    		var finder = identMult();

		for (String query : queries) {
      			finder = finder.and(Finder.contains(query));
    		}
    		return finder;
  	}

	// 扩展查询。 寻找替代品。
	public static Finder expandedFinder(String... queries) {
    		var finder = identSum();

    		for (String query : queries) {
      			finder = finder.or(Finder.contains(query));
    		}
   		return finder;
  	}
	...
}

创建一个处理这些组合器的应用程序

var queriesOr = new String[]{"many", "Annabel"};
var finder = Finders.expandedFinder(queriesOr);
var res = finder.find(text());
LOGGER.info("the result of expanded(or) query[{}] is {}", queriesOr, res);

var queriesAnd = new String[]{"Annabel", "my"};
finder = Finders.specializedFinder(queriesAnd);
res = finder.find(text());
LOGGER.info("the result of specialized(and) query[{}] is {}", queriesAnd, res);

finder = Finders.advancedFinder("it was", "kingdom", "sea");
res = finder.find(text());
LOGGER.info("the result of advanced query is {}", res);

res = Finders.filteredFinder(" was ", "many", "child").find(text());
LOGGER.info("the result of filtered query is {}", res);

private static String text() {
    return
        "It was many and many a year ago,\n"
            + "In a kingdom by the sea,\n"
            + "That a maiden there lived whom you may know\n"
            + "By the name of ANNABEL LEE;\n"
            + "And this maiden she lived with no other thought\n"
            + "Than to love and be loved by me.\n"
            + "I was a child and she was a child,\n"
            + "In this kingdom by the sea;\n"
            + "But we loved with a love that was more than love-\n"
            + "I and my Annabel Lee;\n"
            + "With a love that the winged seraphs of heaven\n"
            + "Coveted her and me.";
  }

程序输出

the result of expanded(or) query[[many, Annabel]] is [It was many and many a year ago,, By the name of ANNABEL LEE;, I and my Annabel Lee;]
the result of specialized(and) query[[Annabel, my]] is [I and my Annabel Lee;]
the result of advanced query is [It was many and many a year ago,]
the result of filtered query is [But we loved with a love that was more than love-]

我们也可以设计我们的应用程序，使其具有查询查找功能expandedFinder, specializedFinder, advancedFinder, filteredFinder，这些功能均派生自contains, or, not, and。 

🔍类图 

Combinator class diagram 

🔍适用场景

在以下情况下使用组合器模式：

🔍优点