java小知识3(多态)
多态不能调用子类的特有方法只能调用重写的方法；方法编译也是看左边，但运行看右边 ------------------------------------ 想用子类特有功能需要强转，但不能乱转，可以用instanceof判断
java小知识2(接口)
12345678910111213141516171819202122232425public abstract class Animal { private String name; private int age; public Animal() { } public Animal(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)...
java小知识1(多态中调用成员方法和变量的区别)
多态中调用成员方法和变量的区别:123456789101112131415161718192021222324252627public class Test { public static void main(String[] args) { Animal a=new Dog(); //调用成员变量:编译看左边,运行看左边 //如果左边的类中没有,就会向上找,直到找到为止 //如果没有找到,就会报错 System.out.println(a.name);//动物 //调用成员方法:编译看左边,运行看右边 //如果左边的类中没有,就会向上找,直到找到为止 //如果没有找到,就会报错 //但是运行时调用的是右边的方法 a.show();//Dog---show }}class Animal{ String name="动物"; public void...
Hello World
Welcome to Hexo! This is your very first post. Check documentation for more info. If you get any problems when using Hexo, you can find the answer in troubleshooting or you can ask me on GitHub. Quick StartCreate a new post1$ hexo new "My New Post" More info: Writing Run server1$ hexo server More info: Server Generate static files1$ hexo generate More info: Generating Deploy to remote sites1$ hexo deploy More info: Deployment
java小知识
子类可以调用本类的有参构造父类的构造方法不能调用要用super();set和get方法不属于构造方法,可以调用 12345678910111213141516class Student { String name; int age; // 无参构造 public Student() { this("Tom", 18); // 调用本类的有参构造 } // 有参构造 public Student(String name, int age) { this.name = name; this.age = age; }} 👉 这里就是：子类还没出现，先说明“本类构造可以调本类构造” 示例：父类 + 子类123456789101112131415161718192021class Father { int money; public Father(int money) { ...
小项目1
1234567891011121314151617181920212223242526272829303132333435363738394041424344454647484950public class User { private String username; private String password; private String id; private String phoneNumber; public User() { } public User(String username, String password, String id, String phoneNumber) { this.username = username; this.password = password; this.id = id; this.phoneNumber = phoneNumber; } ...
文章标题
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