JAVA设计模式-策略模式demo

向右看齐 2022-03-01 02:44 149阅读 0赞

### 说明 ###

下面以为JSONArray的排序为例子。将排序的规则封装成一个个算法（Comparator），通过修改规则的具体实现，可以改变排序结果。

### 代码 ###

package com.ydfind.demo.designmode;
    
    import com.alibaba.fastjson.JSON;
    import com.alibaba.fastjson.JSONArray;
    import com.alibaba.fastjson.JSONObject;
    import org.slf4j.Logger;
    import org.slf4j.LoggerFactory;
    
    import java.util.Collections;
    import java.util.Comparator;
    import java.util.LinkedList;
    
    /**
     * 以为JSONArray的排序为例子。将排序的规则封装成一个个算法，通过修改规则的具体实现算法，可以改变排序
     */
    public class StrategyDemo {
        private static Logger logger = LoggerFactory.getLogger(StrategyDemo.class);
        public static Comparator<JSONObject> getIntComparator(final String key){
            return new Comparator<JSONObject>() {
                @Override
                public int compare(JSONObject o1, JSONObject o2) {
                    int i1 = o1.getIntValue(key);
                    int i2 = o2.getIntValue(key);
                    if(i1 == i2){
                        return 0;
                    }else {
                        return i1 > i2 ? 1 : -1;
                    }
                }
            };
        }
        public static Comparator<JSONObject> getStrComparator(final String key){
            return new Comparator<JSONObject>() {
                @Override
                public int compare(JSONObject o1, JSONObject o2) {
                    String str1 = o1.getString(key);
                    String str2 = o2.getString(key);
                    return str1.compareToIgnoreCase(str2);
                }
            };
        }
        public static void sort(JSONArray jsonArray, String key, Comparator comparator){
            LinkedList<Object> list = new LinkedList<Object>();
            for(int i = 0; i < jsonArray.size(); i++){
                list.add(jsonArray.get(i));
            }
            Collections.sort(list, comparator);
            jsonArray.clear();
            for(int i = 0; i < list.size(); i++){
                jsonArray.add(list.get(i));
            }
            list = null;
        }
        public static void main(String[] args){
            String jsonStr = "[{\"int\": \"1\",\"str\": \"z\"},{\"int\": \"4\",\"str\": \"q\"},{\"int\": \"2\",\"str\": \"y\"},{\"int\": \"5\", \"str\": \"o\"},{\"int\": \"3\", \"str\": \"x\"}]";
            JSONArray jsonArray = JSON.parseArray(jsonStr);
            logger.info("--------按整型int排序------------------------------------");
            sort(jsonArray, "int", getIntComparator("int"));
            for(int i = 0; i < jsonArray.size(); i++){
                logger.info("第" + i + "元素 = " + jsonArray.get(i).toString());
            }
            logger.info("--------按String排序------------------------------------");
            sort(jsonArray, "str", getStrComparator("str"));
            for(int i = 0; i < jsonArray.size(); i++){
                logger.info("第" + i + "元素 = " + jsonArray.get(i).toString());
            }
        }
    }

### maven依赖 ###

<dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>fastjson</artifactId>
            <version>1.2.47</version>
        </dependency>

### 运行结果 ###

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3NuZGF5WVU_size_16_color_FFFFFF_t_70]

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