目录结构

对于使用ArrayList集合并使用Iterator遍历

package test2;
import java.util.ArrayList;
import java.util.Iterator;

public class T8 {
    public static void main(String[] args) {
        // 创建ArrayList集合并添加元素
        ArrayList<String> arrayList = new ArrayList<>();
        arrayList.add("Java");
        arrayList.add("Python");
        arrayList.add("C++");
        arrayList.add("JavaScript");
        arrayList.add("Ruby");
        arrayList.add("Swift");
        arrayList.add("Kotlin");
        arrayList.add("Go");
        arrayList.add("Rust");
        arrayList.add("TypeScript教程");

        // 使用Iterator遍历ArrayList
        Iterator<String> iterator = arrayList.iterator();
        while (iterator.hasNext()) {
            String element = iterator.next();
            System.out.println(element);
        }
    }
}

运行结果

在HashSet集合中添加Person对象

package test2;
import java.util.HashSet;

class Person {
    private String name;
    private int age;

    public Person(String name, int age) {
        this.name = name;
        this.age = age;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

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

    @Override
    public boolean equals(Object obj) {
        if (this == obj) return true;
        if (obj == null || getClass() != obj.getClass()) return false;
        Person person = (Person) obj;
        return name.equals(person.name);
    }
}

public class T82 {
    public static void main(String[] args) {
        // 创建HashSet集合并添加Person对象
        HashSet<Person> personSet = new HashSet<>();
        personSet.add(new Person("张三", 25));
        personSet.add(new Person("李四", 30));
        personSet.add(new Person("张三", 25));  // 不会被重复添加

        // 打印HashSet中的Person对象
        for (Person person : personSet) {
            System.out.println("Name: " + person.getName() + ", Age: " + person.getAge());
        }
    }
}

运行结果

使用TreeMap按学号的自然顺序的倒序打印键值对

package test2;

import java.util.*;

public class T83 {
    public static void main(String[] args) {
        // 创建TreeMap集合并存储学号和姓名
        TreeMap<Integer, String> studentMap = new TreeMap<>();
        studentMap.put(101, "张三");
        studentMap.put(103, "李四");
        studentMap.put(105, "王五");
        studentMap.put(102, "贾六");
        studentMap.put(104, "吴七");

        // 打乱顺序观察排序效果
        System.out.println("乱序输出:");
        for (Map.Entry<Integer, String> entry : studentMap.entrySet()) {
            System.out.println("学号: " + entry.getKey() + ", 姓名: " + entry.getValue());
        }
      
        TreeMap<Integer, String> reverseStudentMap = new TreeMap<>(Comparator.reverseOrder());
        reverseStudentMap.putAll(studentMap);

        // 打印倒序后的键值对
        System.out.println("\n倒序输出:");
        for (Map.Entry<Integer, String> entry : reverseStudentMap.entrySet()) {
            System.out.println("学号: " + entry.getKey() + ", 姓名: " + entry.getValue());
        }
    }
}

运行结果