java8 stream处理集合

刺骨的言语ヽ痛彻心扉 2022-03-06 09:52 458阅读 0赞

**实体类**

package com.ahut.common.utils.bean;
    
    import java.math.BigDecimal;
    
    /**
     * desc : 接口监控实体
     * create_user : cheng
     * create_date : 2019/3/15 10:37
     */
    public class InterfaceMonitorEntity {
    
        /**
         * 接口名称
         */
        private String interfaceName;
        /**
         * 状态码
         */
        private int status;
        /**
         * 调用次数
         */
        private int callCount;
        /**
         * 分数
         */
        private BigDecimal score;
    
        public InterfaceMonitorEntity(String interfaceName, int status, int callCount, BigDecimal score) {
            this.interfaceName = interfaceName;
            this.status = status;
            this.callCount = callCount;
            this.score = score;
        }
    
        @Override
        public String toString() {
            return "InterfaceMonitorEntity{" +
                    "interfaceName='" + interfaceName + '\'' +
                    ", status=" + status +
                    ", callCount=" + callCount +
                    ", score=" + score +
                    '}';
        }
    
        public String getInterfaceName() {
            return interfaceName;
        }
    
        public void setInterfaceName(String interfaceName) {
            this.interfaceName = interfaceName;
        }
    
        public int getStatus() {
            return status;
        }
    
        public void setStatus(int status) {
            this.status = status;
        }
    
        public int getCallCount() {
            return callCount;
        }
    
        public void setCallCount(int callCount) {
            this.callCount = callCount;
        }
    
        public BigDecimal getScore() {
            return score;
        }
    
        public void setScore(BigDecimal score) {
            this.score = score;
        }
    }

## 单字段分组 ##

@Test
        public void testGroupBy() {
            List<InterfaceMonitorEntity> monitorList = new ArrayList<>(5);
    
            monitorList.add(new InterfaceMonitorEntity("create", 0, 1000, new BigDecimal(1)));
            monitorList.add(new InterfaceMonitorEntity("create", -1, 1, new BigDecimal(1)));
            monitorList.add(new InterfaceMonitorEntity("delete", 0, 10, new BigDecimal(1)));
            monitorList.add(new InterfaceMonitorEntity("update", 0, 100, new BigDecimal(1)));
            monitorList.add(new InterfaceMonitorEntity("search", 0, 10000, new BigDecimal(1)));
            monitorList.add(new InterfaceMonitorEntity("search", 0, 10001, new BigDecimal(1)));
            monitorList.add(new InterfaceMonitorEntity("search", -1, 10002, new BigDecimal(1)));
    
            // 单字段分组(依据interfaceName进行分组)
            Map<String, List<InterfaceMonitorEntity>> monitorMap1 = monitorList.stream().collect(Collectors.groupingBy(InterfaceMonitorEntity::getInterfaceName));
            for (Map.Entry<String, List<InterfaceMonitorEntity>> entry : monitorMap1.entrySet()) {
                System.out.println(entry.getKey() + " : " + entry.getValue());
            }
    	}

输出

search : [InterfaceMonitorEntity{interfaceName='search', status=0, callCount=10000}, InterfaceMonitorEntity{interfaceName='search', status=0, callCount=10001}, InterfaceMonitorEntity{interfaceName='search', status=-1, callCount=10002}]
    update : [InterfaceMonitorEntity{interfaceName='update', status=0, callCount=100}]
    create : [InterfaceMonitorEntity{interfaceName='create', status=0, callCount=1000}, InterfaceMonitorEntity{interfaceName='create', status=-1, callCount=1}]
    delete : [InterfaceMonitorEntity{interfaceName='delete', status=0, callCount=10}]

## 多字段分组 ##

@Test
        public void testGroupBy() {
            List<InterfaceMonitorEntity> monitorList = new ArrayList<>(5);
    
            monitorList.add(new InterfaceMonitorEntity("create", 0, 1000, new BigDecimal(1)));
            monitorList.add(new InterfaceMonitorEntity("create", -1, 1, new BigDecimal(1)));
            monitorList.add(new InterfaceMonitorEntity("delete", 0, 10, new BigDecimal(1)));
            monitorList.add(new InterfaceMonitorEntity("update", 0, 100, new BigDecimal(1)));
            monitorList.add(new InterfaceMonitorEntity("search", 0, 10000, new BigDecimal(1)));
            monitorList.add(new InterfaceMonitorEntity("search", 0, 10001, new BigDecimal(1)));
            monitorList.add(new InterfaceMonitorEntity("search", -1, 10002, new BigDecimal(1)));
    
            // 多字段分组
            Map<String, List<InterfaceMonitorEntity>> monitorMap2 = monitorList.stream().collect(Collectors.groupingBy(this::multiField));
            for (Map.Entry<String, List<InterfaceMonitorEntity>> entry : monitorMap2.entrySet()) {
                System.out.println(entry.getKey() + " : " + entry.getValue());
            }
    	}
    	
        /**
         * desc : 组合字段
         * create_user : cheng
         * create_date : 2019/3/18 16:13
         */
        private String multiField(InterfaceMonitorEntity entity) {
            return entity.getInterfaceName() + entity.getStatus();
        }

输出

update0 : [InterfaceMonitorEntity{interfaceName='update', status=0, callCount=100}]
    create-1 : [InterfaceMonitorEntity{interfaceName='create', status=-1, callCount=1}]
    search0 : [InterfaceMonitorEntity{interfaceName='search', status=0, callCount=10000}, InterfaceMonitorEntity{interfaceName='search', status=0, callCount=10001}]
    create0 : [InterfaceMonitorEntity{interfaceName='create', status=0, callCount=1000}]
    search-1 : [InterfaceMonitorEntity{interfaceName='search', status=-1, callCount=10002}]
    delete0 : [InterfaceMonitorEntity{interfaceName='delete', status=0, callCount=10}]

## 分组统计数量 ##

@Test
        public void testGroupBy() {
            List<InterfaceMonitorEntity> monitorList = new ArrayList<>(5);
    
            monitorList.add(new InterfaceMonitorEntity("create", 0, 1000, new BigDecimal(1)));
            monitorList.add(new InterfaceMonitorEntity("create", -1, 1, new BigDecimal(1)));
            monitorList.add(new InterfaceMonitorEntity("delete", 0, 10, new BigDecimal(1)));
            monitorList.add(new InterfaceMonitorEntity("update", 0, 100, new BigDecimal(1)));
            monitorList.add(new InterfaceMonitorEntity("search", 0, 10000, new BigDecimal(1)));
            monitorList.add(new InterfaceMonitorEntity("search", 0, 10001, new BigDecimal(1)));
            monitorList.add(new InterfaceMonitorEntity("search", -1, 10002, new BigDecimal(1)));
    
            // 分组统计
            Map<String, Long> monitorMap3 = monitorList.stream().collect(Collectors.groupingBy(InterfaceMonitorEntity::getInterfaceName, Collectors.counting()));
            for (Map.Entry<String, Long> entry : monitorMap3.entrySet()) {
                System.out.println(entry.getKey() + " : " + entry.getValue());
            }
        }

输出

search : 3
    update : 1
    create : 2
    delete : 1

## 多字段排序 ##

@Test
        public void testGroupBy() {
            List<InterfaceMonitorEntity> monitorList = new ArrayList<>(5);
    
            monitorList.add(new InterfaceMonitorEntity("create", 0, 1000, new BigDecimal(1)));
            monitorList.add(new InterfaceMonitorEntity("create", -1, 1, new BigDecimal(2)));
            monitorList.add(new InterfaceMonitorEntity("delete", 0, 10, new BigDecimal(3)));
            monitorList.add(new InterfaceMonitorEntity("update", 0, 100, new BigDecimal(1)));
            monitorList.add(new InterfaceMonitorEntity("search", 0, 10000, new BigDecimal(1)));
            monitorList.add(new InterfaceMonitorEntity("search", 0, 10001, new BigDecimal(1)));
            monitorList.add(new InterfaceMonitorEntity("search", -1, 10002, new BigDecimal(1)));
                    
            // 多字段排序
            monitorList.stream()
                    .sorted(Comparator.comparing(InterfaceMonitorEntity::getStatus)
                            .thenComparing(InterfaceMonitorEntity::getCallCount)
                            .thenComparing(InterfaceMonitorEntity::getScore))
                    .forEach(System.out::println);
        }

输出

InterfaceMonitorEntity{interfaceName='create', status=-1, callCount=1, score=2}
    InterfaceMonitorEntity{interfaceName='search', status=-1, callCount=10002, score=1}
    InterfaceMonitorEntity{interfaceName='delete', status=0, callCount=10, score=3}
    InterfaceMonitorEntity{interfaceName='update', status=0, callCount=100, score=1}
    InterfaceMonitorEntity{interfaceName='create', status=0, callCount=1000, score=1}
    InterfaceMonitorEntity{interfaceName='search', status=0, callCount=10000, score=1}
    InterfaceMonitorEntity{interfaceName='search', status=0, callCount=10001, score=1}

## 倒序排序 ##

@Test
        public void testGroupBy() {
            List<InterfaceMonitorEntity> monitorList = new ArrayList<>(5);
    
            monitorList.add(new InterfaceMonitorEntity("create", 0, 1000, new BigDecimal(1)));
            monitorList.add(new InterfaceMonitorEntity("create", -1, 1, new BigDecimal(2)));
            monitorList.add(new InterfaceMonitorEntity("delete", 0, 10, new BigDecimal(3)));
            monitorList.add(new InterfaceMonitorEntity("update", 0, 100, new BigDecimal(1)));
            monitorList.add(new InterfaceMonitorEntity("search", 0, 10000, new BigDecimal(1)));
            monitorList.add(new InterfaceMonitorEntity("search", 0, 10001, new BigDecimal(1)));
            monitorList.add(new InterfaceMonitorEntity("search", -1, 10002, new BigDecimal(1)));
    
            // 多字段排序
            monitorList.stream()
                    .sorted(Comparator.comparing(InterfaceMonitorEntity::getCallCount).reversed())
                    .forEach(System.out::println);
        }

输出

InterfaceMonitorEntity{interfaceName='search', status=-1, callCount=10002, score=1}
    InterfaceMonitorEntity{interfaceName='search', status=0, callCount=10001, score=1}
    InterfaceMonitorEntity{interfaceName='search', status=0, callCount=10000, score=1}
    InterfaceMonitorEntity{interfaceName='create', status=0, callCount=1000, score=1}
    InterfaceMonitorEntity{interfaceName='update', status=0, callCount=100, score=1}
    InterfaceMonitorEntity{interfaceName='delete', status=0, callCount=10, score=3}
    InterfaceMonitorEntity{interfaceName='create', status=-1, callCount=1, score=2}