java ArrayList的遍历

发布于2021-11-25 20:43 阅读(352) 评论(0) 点赞(20) 收藏(2)

1.定义一个User类，属性有姓名，年龄，性别（性别用字符类型表示，m表示男，f表示女），电话，住址，定义初始化属性的构造方法，定义打印输出所有用户信息的show方法

2.定义一个管理User的类UserManager类，使用ArrayList对象管理所有的用户，完成用户的添加，删除，以及查找，同时统计用户的平均年龄，统计注册用户男性和女性的数量。

3.定义测试类，测试类中各功能

ArrayList的遍历可以采用下面的3种方式进行遍历。


方法一：
		for(int i=0;i<list1.size();i++){
			System.out.println(list1.get(i));
		}
		
方法二：
		Object o[] = list1.toArray();
		for(int i=0;i<o.length;i++){
			String temp = (String)o[i];
			System.out.println(temp);
		}
		
方法三：
		Iterator<String> i = list1.iterator();
		while(i.hasNext()){
			String temp = i.next();
			System.out.println(temp);
		}

下面程序用两种方式实现：

第一种方式实现：

User代码实现：


public class User {
	String name;
	int age;
	String sex;
	String phone;
	String address;
 
	public User(String name, int age, String sex, String phone, String address) {
		super();
		this.name = name;
		this.age = age;
		this.sex = sex;
		this.phone = phone;
		this.address = address;
	}
 
	void show() {
		System.out.println(
				"姓名：" + name + "" + "年龄：" + age + "" + "姓别：" + sex + "" + "电话：" + phone + "" + "住址：" + address + "");
	}
}

测试类代码：


public class UserManager {
	public static void main(String[] args) {
		ArrayList<User> list = new ArrayList<User>();// 泛型
		// ArrayList<String> strList = new ArrayList<String>();
		User u1 = new User("张一", 20, "m", "12345961455", "大连");
		User u2 = new User("张二", 22, "f", "12495361460", "旅顺");
		User u3 = new User("张三", 29, "m", "12741261471", "小日子");
		User u4 = new User("张四", 25, "f", "12789921472", "北京");
		User u5 = new User("张五", 24, "m", "12345961778", "大庆");
		// 添加
		list.add(u1);
		list.add(u2);
		list.add(u3);
		list.add(u4);
		list.add(u5);
		// 查找
		for (int i = 0; i < list.size(); i++) {
			list.get(i).show();
		}
		// 删除
		list.remove(1);
		int sum = 0, avg = 0, numm = 0, numf = 0;
		System.out.println("--------------------------");
		for (int i = 0; i < list.size(); i++) {
			list.get(i).show();
			// 统计平均年龄,注册用户的男性和女性数量
			// 年龄总和
			sum += list.get(i).age;
			// 平均年龄
			avg = sum / list.size();
			// 注册用户的男性和女性数量
			if (list.get(i).sex == "m") {
				numm += 1;
			}
			if (list.get(i).sex == "f") {
				numf += 1;
			}
		}
		System.out.println("--------------------------");
		System.out.println("平均年龄为：" + avg);
		System.out.println("--------------------------");
		System.out.println("男性数量：" + numm);
		System.out.println("女性数量：" + numf);
	}
}

效果实现：

第二种方式实现：


public class UserManagerTest {
 
	public static void main(String[] args) {
		UserManager um = new UserManager();
		User u1 = new User("张三", 20, 'm', "13408094567", "东软");
		User u2 = new User("李四", 22, 'f', "13408094567", "东软");
		User u3 = new User("王五", 21, 'f', "13408094567", "东软");
		um.addUser(u1);
		um.addUser(u2);
		um.addUser(u3);
 
		um.showUserList();
		um.removeUser(u3);
		System.out.println("移除一个用户后：");
		um.showUserList();
		User u4 = new User("王五", 21, 'f', "13408094567", "东软");
		System.out.println("查找用户：" + um.findUser(u4));
		System.out.println("平均年龄：" + um.averageAge());
		System.out.println("女性：" + um.getFemaleCount() + "人");
		System.out.println("男性：" + um.getMaleCount() + "人");
	}
 
}
 
class User {
	String name;
	int age;
	char sex;
	String telephone;
	String address;
 
	User(String name, int age, char sex, String telephone, String address) {
		this.name = name;
		this.age = age;
		this.sex = sex;
		this.telephone = telephone;
		this.address = address;
	}
 
	void show() {
		System.out.println(
				"name:" + name + "，age:" + age + "，sex:" + sex + "，telephone:" + telephone + "，address:" + address);
	}
}
 
class UserManager {
	ArrayList<User> userList;
 
	public void addUser(User u) {
		if (userList == null) {
			userList = new ArrayList<User>();
		}
 
		userList.add(u);
	}
 
	public void showUserList() {
		if (userList == null) {
			System.out.println("无任何用户");
		} else {
			for (int i = 0; i < userList.size(); i++) {
				User temp = (User) userList.get(i);
				temp.show();
			}
		}
	}
 
	public void removeUser(User u) {
		if (userList != null) {
			userList.remove(u);
		}
	}
 
	public boolean findUser(User u) {
		if (userList != null) {
			return userList.contains(u);
		} else {
			return false;
		}
	}
 
	// 平均年龄
	public double averageAge() {
		double sum = 0;
		if (userList == null) {
			System.out.println("无任何用户,无法计算平均年龄");
			return -1;
		} else {
			for (int i = 0; i < userList.size(); i++) {
				User temp = (User) userList.get(i);
				sum += temp.age;
			}
			return sum / userList.size();
		}
	}
 
	// 女性
	public int getFemaleCount() {
		int sum = 0;
		if (userList == null) {
			System.out.println("无任何用户,无法计算女性数量");
		} else {
			for (int i = 0; i < userList.size(); i++) {
				User temp = userList.get(i);
				if (temp.sex == 'f') {
					sum++;
				}
			}
		}
		return sum;
	}
 
	// 男性
	public int getMaleCount() {
		int sum = 0;
		if (userList == null) {
			System.out.println("无任何用户,无法计算男性数量");
		} else {
			for (int i = 0; i < userList.size(); i++) {
				User temp = userList.get(i);
 
				if (temp.sex == 'm') {
					sum++;
				}
			}
		}
		return sum;
	}
}