Java 数据类型参考

public class BasicTypesDemo {
public static void main(String\[] args) {
// 基本数据类型
int userCount = 120;                // 整数类型
double cpuLoad = 0.85;              // 浮点数类型
char status = 'A';                  // 字符类型
boolean isActive = true;            // 布尔类型

// 引用数据类型
String serverName = "Node-Backend"; // 字符串对象
Integer maxConn = Integer.valueOf(500); // 包装类对象

// 输出演示
System.out.println("服务器名称: " + serverName);
System.out.println("用户数量: " + userCount);
System.out.println("CPU 负载: " + cpuLoad);
System.out.println("状态: " + status);
System.out.println("是否激活: " + isActive);
System.out.println("最大连接数: " + maxConn);
}

}

class User {
private String username;
private int age;
private boolean active;

public User(String username, int age, boolean active) {
this.username = username;
this.age = age;
this.active = active;
}

public String getUsername() { return username; }
public int getAge() { return age; }
public boolean isActive() { return active; }

@Override
public String toString() {
return "User{" + "username='" + username + '\'' +
", age=" + age + ", active=" + active + '}';
}

}

public class PracticalTypesDemo {
public static void main(String\[] args) {
User\[] users = {
new User("Alice", 28, true),
new User("Bob", 35, false),
new User("Charlie", 22, true)
};

// 简单算法：筛选活跃用户
for (User user : users) {
if (user.isActive()) {
System.out.println("活跃用户: " + user);
}
}
}

}

import java.util.ArrayList;
import java.util.List;

class Order {
private int orderId;
private double amount;
private String status;

public Order(int orderId, double amount, String status) {
if (amount < 0) throw new IllegalArgumentException("金额不能为负数");
this.orderId = orderId;
this.amount = amount;
this.status = status;
}

public double getAmount() { return amount; }
public String getStatus() { return status; }

@Override
public String toString() {
return "Order{" + "orderId=" + orderId +
", amount=" + amount + ", status='" + status + '\'' + '}';
}

}

public class AdvancedTypesDemo {
public static void main(String\[] args) {
List<Order> orders = new ArrayList<>();
orders.add(new Order(1001, 250.75, "CONFIRMED"));
orders.add(new Order(1002, 499.99, "SHIPPED"));
orders.add(new Order(1003, 120.00, "CANCELLED"));

double totalRevenue = 0;
for (Order order : orders) {
if (!order.getStatus().equals("CANCELLED")) {
totalRevenue += order.getAmount();
}
}
System.out.println("有效订单总收入: " + totalRevenue);
}

}