Jupyter Notebook之移除anaconda环境

项目场景：

java stream distinct根据list某个字段去重，普通List简单去重：

import java.util.Arrays;
import java.util.List;
import java.util.stream.Collectors;

public class TestMain {
	public static void main(String[] args) {
        List<String> names = Arrays.asList("张三", "李四", "王五", "张三", "李四");
        
        // 使用Stream的distinct()方法进行去重操作
        List<String> distinctNames = names.stream().distinct().collect(Collectors.toList());

        System.out.println("原始列表：" + names);
        System.out.println("去重后的列表：" + distinctNames);
    }
}

很显然这种满足不了需求，我们List里的是实体对象，这里的是字符串。

前提基础： 

import lombok.Data;

@Data
public class Student {
	
    public Student(Integer id, String name, Integer age) {
		this.id = id;
		this.name = name;
		this.age = age;
	}
    
	private Integer id;
    private String name;
    private Integer age;
}

解决方案：

一、Stream流 + TreeSet（推荐）

import java.util.ArrayList;
import java.util.Comparator;
import java.util.List;
import java.util.TreeSet;
import java.util.stream.Collectors;

public class TestMain {
	public static void main(String[] args) {
		List<Student> list = new ArrayList<>();
		list.add(new Student(1, "张三", 13));
		list.add(new Student(2, "李四", 14));
		list.add(new Student(3, "张三", 15));
		list.add(new Student(4, "王五", 16));
		list.add(new Student(5, "李四", 17));

		List<Student> distinctList = list.stream().collect(
		    Collectors.collectingAndThen(
		        Collectors.toCollection(() -> new TreeSet<>(Comparator.comparing(Student::getName))), ArrayList<Student>::new)
		);
		System.out.println(distinctList);
    }
}

二、Stream流 + toMap

import java.util.ArrayList;
import java.util.List;
import java.util.function.Function;
import java.util.stream.Collectors;

public class TestMain {
	public static void main(String[] args) {
		List<Student> list = new ArrayList<>();
		list.add(new Student(1, "张三", 13));
		list.add(new Student(2, "李四", 14));
		list.add(new Student(3, "张三", 15));
		list.add(new Student(4, "王五", 16));
		list.add(new Student(5, "李四", 17));

		List<Student> distinctList = list.stream()
		        .collect(Collectors.toMap(Student::getName, Function.identity(), (p1, p2) -> p1))
		        .values()
		        .stream()
		        .collect(Collectors.toList());
		
		System.out.println(distinctList);
    }
}

三、重写equals和hashCode

Student类在原来的基础上，重写equals和hashCode，根据学生的name去重

import java.util.Objects;
import lombok.Data;

@Data
public class Student {
	
    public Student(Integer id, String name, Integer age) {
		this.id = id;
		this.name = name;
		this.age = age;
	}
    
	private Integer id;
    private String name;
    private Integer age;
    
    // 重写 equals 和 hashCode 方法
    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        Student student = (Student) o;
        return Objects.equals(name, student.name);
    }

    @Override
    public int hashCode() {
        return Objects.hash(name);
    }
}

import java.util.ArrayList;
import java.util.List;
import java.util.stream.Collectors;

public class TestMain {
	public static void main(String[] args) {
		List<Student> list = new ArrayList<>();
		list.add(new Student(1, "张三", 13));
		list.add(new Student(2, "李四", 14));
		list.add(new Student(3, "张三", 15));
		list.add(new Student(4, "王五", 16));
		list.add(new Student(5, "李四", 17));

		List<Student> distinctList = list.stream().distinct().collect(Collectors.toList());
		
		System.out.println(distinctList);
    }
}