Class and Object

• Class: a bluepoint for a data type, scheme
• Object: a specific realization of any class, instance

public class Employee {
    // static 所有员工共享同一个bonusRate
    static double bonusRate = 0.1; 

    // final Read Only 
    final String name; // final 初始化 thread safe
    final String id;   
    int age;
    int salary;
    int level;

    Employee(String name, int age, String id, int level) {
        this.name = name;
        this.age = age;
        this.id = id;
        this.level = level;
    }
}