java基础之set集合练习（HashSet，LinkedHashSet，TreeSet）

1：完成以下填空：

Collection 接口的特点是 ????存放list与set共性内容 没有直接实现类 ?没有明确的存储特点要求 ?????????;

2：List 接口的特点是元素 有 （有|无）顺序，?可 （可以|不可以）重复；

Set 接口的特点是元素 无 （有|无）顺序，不可? （可以|不可以）重复；

3：(Set)关于Set 集合描述正确的是（）

A.可以利用Set 创建集合对象，存储多个对象

B.可以利用下标操作集合中的数据

C.Set 集合中所有方法继承于父接口Collection

D.以上描述都不正确

4：(List、Set)仔细阅读以下程序，关于程序描述正确的是（）

A.编译不通过 B． 编译通过，运行时异常

C． 编译运行都正常，输出 3 D． 编译运行都正常，输出 4

5：(Set)仔细阅读以下代码，将不正确的代地方进行改正。

hashCode里面的salary 前面加强转（int）

?Equals 里面

Public boolean equals (Object o){

?????If(this == o) return true;

?????If(this.getClass != o.getClass || o == null) return false;

Worker w = (Worker)o;

?????return name.equals(o.Name) && salary == w.salary && age ==w.age;

}

将第三个add的0删掉，set的集合不能用下标赋值

6：(Set)编程：创建一个商品(Product)类,属性：商品名，商品单价，商品的数量，商品产地。

①创建多个商品对象，存储在 Set 集合中，集合中不能出现重复商品，商品名相同即为重复，在 Product 类中添加必要的方法；

②显示所有的商品信息；

③打印输出商品价格 > 1000 的所有商品信息；

④打印售空的商品的信息；

⑤打印输出商品产地为"北京"的商品信息；

⑥输入一个商品名，查询出此类商品的信息，如果不存在，则打印商品"商场无此商品！！！"

⑦输入一个价格段，查询出集合中所有在这个价格区间的所有商品信息。

public class Product {
????private String goosName;
????private double price;
????private int quantity;//数量
????private String area;

????public Product() {
????}

????public Product(String goosName, double price, int quantity, String area) {
????????this.goosName = goosName;
????????this.price = price;
????????this.quantity = quantity;
????????this.area = area;
????}

????public String getGoosName() {
????????return goosName;
????}

????public void setGoosName(String goosName) {
????????if(!this.goosName.equals(goosName)){
????????????this.goosName = goosName;
????????}
????}

????public double getPrice() {
????????return price;
????}

????public void setPrice(double price) {
????????this.price = price;
????}

????public int getQuantity() {
????????return quantity;
????}

????public void setQuantity(int quantity) {
????????this.quantity = quantity;
????}

????public String getArea() {
????????return area;
????}

????public void setArea(String area) {
????????this.area = area;
????}

????@Override
????public String toString() {
????????return "Produtor{" +
????????????????"goosName='" + goosName + '\'' +
????????????????", price=" + price +
????????????????", quantity=" + quantity +
????????????????", area='" + area + '\'' +
????????????????'}';
????}

????@Override
????public boolean equals(Object o) {
????????if (this == o) return true;
????????if (o == null || getClass() != o.getClass()) return false;
????????Product product = (Product) o;
????????return goosName.equals(product.getGoosName());
????}

????@Override
????public int hashCode() {
????????return goosName.hashCode();
????}
}
public class zy_6 {
????public static void main(String[] args) {

????????Set<Product> set = new HashSet<>();
????????set.add(new Product("小米",1000,100,"北京"));
????????set.add(new Product("小米",2000,99,"beijing"));
????????set.add(new Product("红米",3000,100,"杭州"));
????????set.add(new Product("锤子",4000,0,"苏州"));

????????set.forEach(p -> System.out.println(p));

????????for (Product product : set) {
????????????if(product.getPrice()>1000){
????????????????System.out.println(product);
????????????}
????????}

????????for (Product product : set) {
????????????if(product.getQuantity() ==0){
????????????????System.out.println(product);
????????????}
????????}

????????for (Product product : set) {
????????????if(product.getArea().equals("北京")){
????????????????System.out.println(product);
????????????}
????????}

????????Scanner sc = new Scanner(System.in);
????????System.out.println("输入要查找的手机品牌");
????????String name = sc.next();
????????boolean flag = false;
????????for (Product product : set) {
????????????if(product.getGoosName().equals(name)){
????????????????System.out.println(product);
????????????????flag = true;
????????????}
????????}
????????if(!flag){
????????????System.out.println("商场无此商品！！！");
????????}



????????System.out.println("7======================");
????????System.out.println("输入要查找的价格区间例如：1000-2000");
????????String price = sc.next();
????????String[] split = price.split("-");
????????int price1 = Integer.parseInt(split[0]);
????????int price2 = Integer.parseInt(split[1]);
????????boolean flag2 = false;
????????for (Product product : set) {
????????????double d = product.getPrice();
????????????if(d > price1 && d<price2){
????????????????System.out.println(product);
????????????????flag2 = true;
????????????}
????????}
????????if(!flag2){
????????????System.out.println("商场没有这个区间的商品！！！");
????????}

????}
}

7;(Set)编程：随机产生 10 个 0~50 之间的整数，存储在集合中，要求集合中的数据不能重复。知识补充： Random rd= new Random(); //Random 位于 java.util 包中

int n = rd.nextInt(n); //0~n -1之间的整数

public class zy_7 {
????public static void main(String[] args) {
????????Set<Integer> set = new HashSet<>();
????????Random r = ?new Random();
????????while (set.size()<50){
????????????int n = r.nextInt(50+1);
????????????set.add(n);
????????}
????????System.out.println(set.size());
????}
}

8；(Set)编程：键盘输入一个字符串，利用集合去除其重复字符，打印输出最终不同的字符。

package com.by.homework4;

import java.util.HashSet;
import java.util.LinkedHashSet;
import java.util.Scanner;
import java.util.Set;

public class Test8 {
????public static void main(String[] args) {
????????Scanner sc=new Scanner(System.in);
????????System.out.println("请输入字符串");
????????String str=sc.next();
????????String []strs=str.split("");
????????Set<String> set=new LinkedHashSet<>();

????????for (int i = 0; i < strs.length; i++) {
????????????set.add(strs[i]);
????????}
????????set.forEach(s -> System.out.print(s));
????}
}

9：使用Set集合完成List练习题的最后一题

public class zy_9 {
????public static void main(String[] args) {

????????Set<Student> set = new HashSet<>();


????????Scanner sc = new Scanner(System.in);
????????while (true){
????????????System.out.println("输入学生信息，格式为：张三/18/男/99.5 ???输入：0退出");
????????????String s = sc.next();
????????????if(s.equals("0")){
????????????????break;
????????????}
????????????String[] ss = s.split("/");
????????????Double score = ss[3].equals("null") ? null : Double.valueOf(ss[3]);
????????????set.add(new Student(ss[0],Integer.parseInt(ss[1]),ss[2],score));
????????}


????????System.out.println("1===================");
????????for (Student s : set) {
????????????if(s.getScore() != null && s.getScore()>=80){
????????????????System.out.println(s);
????????????}
????????}

????????System.out.println("2===================");
????????for (Student s : set) {
????????????if(s.getScore() == null){
????????????????System.out.println("没有参加考试的学生："+s);
????????????}
????????}

????????System.out.println("5===================");
????????Set<Student> set2 = new TreeSet<>(new Comparator<Student>() {
????????????@Override
????????????public int compare(Student o1, Student o2) {
????????????????if(o1.getScore()<o2.getScore()){
????????????????????return 1;
????????????????}else if(o1.getScore()>o2.getScore()){
????????????????????return -1;
????????????????}else {
????????????????????return 0;
????????????????}
????????????}
????????});
????????set2.addAll(set);
????????for (Student student : set2) {
????????????System.out.println(student);
????????}

????}
}