java中hashset和tree set区别

HashSet和TreeSet都是Java中的集合类，但它们有一些不同之处。HashSet是基于哈希表实现的，它不保证元素的顺序，而TreeSet是基于红黑树实现的，它可以保证元素按照升序排列。此外，HashSet的插入、删除和查找操作都是O(1)的，而TreeSet的这些操作则是O(log n)的。因此，如果你需要快速的插入、删除和查找操作，并且不需要保证元素的顺序，那么HashSet是更好的选择；如果你需要保证元素的顺序，那么你应该选择TreeSet。

相关问题

/import java.util.HashSet; import java.util.Objects; import java.util.Set; import java.util.TreeSet; public class Test1 { public static void main(String[] args){ Set<Test.Books> set = new HashSet<>(); TreeSet<Test.Books> tree = new TreeSet<>(); Test.Books books1 = new Test.Books(01,"坤坤成长史",520,"我的心"); Test.Books books2 = new Test.Books(02,"坤坤帅哥",1314,"我的脑子"); Test.Books books3 = new Test.Books(03,"双开门大冰箱",999,"我的幻想"); Test.Books books4 = new Test.Books(01,"坤坤成长史",520,"我的心"); set.add(books1); set.add(books2); set.add(books3); set.add(books4); //TreeSet(): 根据其元素的自然排序进行排序 tree.add(books1); tree.add(books2); tree.add(books3); tree.add(books4); System.out.println("HashSet:"); for(Test.Books s1 : set){ System.out.println(s1.getNumber() + s1.getname() + s1.getPrice() +s1.getPublisher()); } System.out.println("TreeSet:"); for(Test.Books s2 : tree){ System.out.println(s2.getNumber() + s2.getname() + s2.getPrice() +s2.getPublisher()); } } //Set没有带索引的方法 //TreeSet 无参构造方法 自然排序 让元素所属的类实现Comparable接口，重写compareTo方法 //重写方法，注意主要条件和次要条件 static abstract class Books implements Comparable<Books> { private int number; private String name; private double price; private String publisher; public Books(){ } Books(int number,String name,double price,String publisher){ super(); this.number = number; this.name = name; this.price = price; this.publisher = publisher; } public int getNumber(){ return number; } public String getname(){ return name; } public double getPrice() { return price; } public String getPublisher() { return publisher; } @Override public int hashCode() { return 0; } @Override public boolean equals(Object o) { if (this == o) return true; if (o == null || getClass() != o.getClass()) return false; Books books = (Books) o; return number == books.number && Double.compare(books.price, price) == 0 && Objects.equals(name, books.name) && Objects.equals(publisher, books.publisher); } public int compareTo(Books s2){ return 1; } } }请帮我修改

在 Test1 类中，你定义的 Books 类应该是一个具体的类而不是抽象类，因为你在 main 方法中实例化了它。此外，你在 compareTo 方法中返回了固定的值 1，这将导致 TreeSet 不会正确排序。你需要根据主要条件和次要条件来实现 compareTo 方法的逻辑。最后，你可以考虑在 Books 类中实现 hashCode 和 equals 方法，以确保在 Set 中正确处理对象。

下面是修改后的代码：

import java.util.HashSet;
import java.util.Objects;
import java.util.Set;
import java.util.TreeSet;

public class Test1 {
    public static void main(String[] args) {
        Set<Books> set = new HashSet<>();
        TreeSet<Books> tree = new TreeSet<>();

        Books books1 = new Books(01, "坤坤成长史", 520, "我的心");
        Books books2 = new Books(02, "坤坤帅哥", 1314, "我的脑子");
        Books books3 = new Books(03, "双开门大冰箱", 999, "我的幻想");
        Books books4 = new Books(01, "坤坤成长史", 520, "我的心");

        set.add(books1);
        set.add(books2);
        set.add(books3);
        set.add(books4);

        tree.add(books1);
        tree.add(books2);
        tree.add(books3);
        tree.add(books4);

        System.out.println("HashSet:");
        for(Books s1 : set){
            System.out.println(s1.getNumber() + s1.getName() + s1.getPrice() + s1.getPublisher());
        }

        System.out.println("TreeSet:");
        for(Books s2 : tree){
            System.out.println(s2.getNumber() + s2.getName() + s2.getPrice() + s2.getPublisher());
        }
    }

    static class Books implements Comparable<Books> {
        private int number;
        private String name;
        private double price;
        private String publisher;

        public Books(int number, String name, double price, String publisher){
            this.number = number;
            this.name = name;
            this.price = price;
            this.publisher = publisher;
        }

        public int getNumber() {
            return number;
        }

        public String getName() {
            return name;
        }

        public double getPrice() {
            return price;
        }

        public String getPublisher() {
            return publisher;
        }

        @Override
        public int compareTo(Books o) {
            if (this.price != o.price) {
                return Double.compare(this.price, o.price);
            } else if (!this.name.equals(o.name)) {
                return this.name.compareTo(o.name);
            } else {
                return Integer.compare(this.number, o.number);
            }
        }

        @Override
        public int hashCode() {
            return Objects.hash(number, name, price, publisher);
        }

        @Override
        public boolean equals(Object o) {
            if (this == o) return true;
            if (o == null || getClass() != o.getClass()) return false;
            Books books = (Books) o;
            return number == books.number &&
                    Double.compare(books.price, price) == 0 &&
                    Objects.equals(name, books.name) &&
                    Objects.equals(publisher, books.publisher);
        }
    }
}