Java中l(wèi)ist集合stream流去重

1. List單個字段去重

list.stream().distinct().collect(Collectors.toList());

2. List對象集合根據(jù)一個或者多個字段去重

準備類：

@Data
public class Book {
    private Long id;
    private String name;
    private Double price;
}

（1）根據(jù)單字段name去重

bookList.stream().collect(Collectors.collectingAndThen(Collectors.toCollection(() -> new TreeSet<>(Comparator.comparing(Book::getName))), ArrayList::new));

（2）根據(jù)多字段name price去重

bookList.stream().collect(Collectors.collectingAndThen(Collectors.toCollection(() -> new TreeSet<>(Comparator.comparing(book -> book.getName() + "-" + book.getPrice()))), ArrayList::new));

（3）示例

import java.util.ArrayList;
import java.util.Comparator;
import java.util.List;
import java.util.TreeSet;
import java.util.stream.Collectors;
import lombok.Data;
 
@Data
public class Book {
    private Long id;
    private String name;
    private Double price;
 
    public Book(Long id, String name, Double price) {
        this.id = id;
        this.name = name;
        this.price = price;
    }
 
    public static void main(String[] args) {
        List<Book> bookList = new ArrayList<>();
        bookList.add(new Book(1L, "書本1", 1.1));
        bookList.add(new Book(2L, "書本1", 1.1));
        bookList.add(new Book(3L, "書本2", 2.2));
        bookList.add(new Book(4L, "書本2", 4.4));
        // 根據(jù)單字段name去重
        List<Book> bookList1 = bookList.stream().collect(Collectors.collectingAndThen(Collectors.toCollection(() -> new TreeSet<>(Comparator.comparing(Book::getName))), ArrayList::new));
        System.out.println("單字段去重結果：" + bookList1.toString());
        // 根據(jù)多字段name price去重
        List<Book> bookList2 = bookList.stream().collect(Collectors.collectingAndThen(Collectors.toCollection(() -> new TreeSet<>(Comparator.comparing(book -> book.getName() + "-" + book.getPrice()))), ArrayList::new));
        System.out.println("多字段去重結果：" + bookList2.toString());
    }
}

輸出打印結果文章來源地址http://www.zghlxwxcb.cn/news/detail-697856.html

單字段去重結果：[Book(id=1, name=書本1, price=1.1), Book(id=3, name=書本2, price=2.2)]
多字段去重結果：[Book(id=1, name=書本1, price=1.1), Book(id=3, name=書本2, price=2.2), Book(id=4, name=書本2, price=4.4)]

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