标签：pac integer rri list集合 zhang rgb 重写 cti hat
package com.mayikt.stream;
import com.mayikt.entity.UserEntity;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.Optional;
import java.util.Set;
import java.util.stream.Collectors;
import java.util.stream.Stream;
public class Test01 {
public static void main(String[] args) {
List<UserEntity> userEntityList = new ArrayList<>();
userEntityList.add(new UserEntity("mayikt", 20));
userEntityList.add(new UserEntity("meite", 28));
userEntityList.add(new UserEntity("zhangsan", 35));
userEntityList.add(new UserEntity("xiaowei", 16));
userEntityList.add(new UserEntity("xiaowei", 16));
/**
* 创建stream两种方式
* 1.串行流
* 2.并行流
*/
Stream<UserEntity> stream = userEntityList.stream();
/**
* 转换成set集合
*/
Set<UserEntity> userSet = stream.collect(Collectors.toSet());
userSet.forEach(userEntity -> System.out.println(userEntity));
/**
* stream将list转换成map
* list集合只有元素，此处将user的userName作为key，user对象作为value，转map
*/
/*
Map<String, UserEntity> userEntityMap = userSet.stream().collect(Collectors.toMap(new Function<UserEntity, String>() {
@Override
public String apply(UserEntity userEntity) {
return userEntity.getUserName();
}
}, new Function<UserEntity, UserEntity>() {
@Override
public UserEntity apply(UserEntity userEntity) {
return userEntity;
}
}));
*/
Map<String, UserEntity> userEntityMap = userSet.stream()
.collect(Collectors.toMap(userEntity -> userEntity.getUserName(), userEntity -> userEntity));
userEntityMap.forEach((k, v) -> System.out.println(k + "," + v));
/**
* Stream reduce求和
*/
Stream<Integer> integerStream = Stream.of(10, 50, 30 ,20);
Optional<Integer> reduce = integerStream.reduce((a1, a2) -> a1 + a2);
System.out.println(reduce.get());
}
}
注意：stream转set的时候，set是去重的，因此UserEntity要重写equals和hashCode。
UserEntity：
package com.mayikt.entity; import java.util.Objects; public class UserEntity { private String userName; private int age; public UserEntity(String userName, int age) { this.userName = userName; this.age = age; } public String getUserName() { return userName; } public void setUserName(String userName) { this.userName = userName; } public int getAge() { return age; } public void setAge(int age) { this.age = age; } @Override public boolean equals(Object o) { if (this == o) return true; if (o == null || getClass() != o.getClass()) return false; UserEntity that = (UserEntity) o; return age == that.age && Objects.equals(userName, that.userName); } @Override public int hashCode() { return Objects.hash(userName, age); } @Override public String toString() { return "UserEntity{" + "userName=‘" + userName + ‘\‘‘ + ", age=" + age + ‘}‘; } }
标签：pac integer rri list集合 zhang rgb 重写 cti hat
原文地址：https://www.cnblogs.com/tenWood/p/14385961.html
