1.user实体
package com.demo.dto;
public class User {
private Integer id; private String userName;
private String password;
private Integer age;
private long c;
public User() {
super();
// TODO Auto-generated constructor stub
} public User(Integer id, String userName, String password, Integer age) {
super();
this.id = id;
this.userName = userName;
this.password = password;
this.age = age;
} public Integer getId() {
return id;
} public void setId(Integer id) {
this.id = id;
} public String getUserName() {
return userName;
} public void setUserName(String userName) {
this.userName = userName == null ? null : userName.trim();
} public String getPassword() {
return password;
} public void setPassword(String password) {
this.password = password == null ? null : password.trim();
} public Integer getAge() {
return age;
} public void setAge(Integer age) {
this.age = age;
} public long getC() {
return c;
} public void setC(long l) {
this.c = l;
} @Override
public String toString() {
return "User [id=" + id + ", userName=" + userName + ", password=" + password + ", age=" + age + ", c=" + c
+ "]";
}
public static void main(String[] args) {
User u1=new User(1, "aa", "aap", 23);
User u2=new User(2, "aa", "aap", 23);
User u3=new User(3, "bb", "aap", 23);
User u4=new User(4, "cc", "aap", 23);
User u5=new User(5, "cc", "aap", 23);
User u6=new User(6, "cc", "aap", 23);
User u7=new User(7, "aa", "aap", 24);
List<User> list=new ArrayList<User>();
list.add(u1);list.add(u2);list.add(u7);list.add(u3);list.add(u4);list.add(u5);list.add(u6);
//原有list(根据第二个字段:userName和第四个字段:age 统计重复的记录数)
//jdk8的方法统计个数:
Map<String, Map<Integer, Long>> map = list.stream().collect(Collectors.groupingBy(User::getUserName,Collectors.groupingBy(User::getAge,Collectors.counting())));
//jdk8以下:
Map<String,Map<Integer,Long>> map=new HashMap<String,Map<Integer,Long>>();
for (User user1 : list) {
Map<Integer, Long> value=new HashMap<Integer,Long>();
long count=0;
if(map.containsKey(user1.getUserName())){
continue;
}
for(int i=0;i<list.size();i++){
if(user1.getUserName().equals(list.get(i).getUserName())&&user1.getAge()==list.get(i).getAge()){
count+=1;
value.put(user1.getAge(),count);
map.put(user1.getUserName(), value);
}else if(user1.getUserName().equals(list.get(i).getUserName())&&user1.getAge()!=list.get(i).getAge()){
value.put(list.get(i).getAge(),Long.valueOf(1));
map.put(user1.getUserName(), value);
}
}
}
map.forEach((k, v) -> {
System.out.println(k+">>>>"+v);
});
List<User> list2=new ArrayList<User>();
list.forEach(user ->{
map.forEach((k, v) -> {
if(k==user.getUserName()){
Long remove = v.remove(user.getAge());
user.setC(null==remove?0:remove);
}
});
list2.add(user);
});
//遍历最后想要的结果(User中c为统计后的个数，方便前台遍历集合时单元格合并行)
list2.forEach(u ->{
System.out.println(u);
});
}
}备注：运行结果如下
cc>>>>{23=3}
bb>>>>{23=1}
aa>>>>{23=2, 24=1}
User [id=1, userName=aa, password=aap, age=23, c=2]
User [id=2, userName=aa, password=aap, age=23, c=0]
User [id=7, userName=aa, password=aap, age=24, c=1]
User [id=3, userName=bb, password=aap, age=23, c=1]
User [id=4, userName=cc, password=aap, age=23, c=3]
User [id=5, userName=cc, password=aap, age=23, c=0]
User [id=6, userName=cc, password=aap, age=23, c=0]
此处是为了实现如下效果：
