封装class Student2{
private String name; //
private int age; // 3~30
private float score;
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;
}
public float getScore() {
return score;
}
public void setScore(float score) {
this.score = score;
}
}
多态
abstract class Animal{
// 抽象方法:只有声明,没有实现(花括号里面那部分)
public abstract void run();
// 普通方法:声明+实现
public void eat(){
System.out.println("Animal is eating...");
}
}
继承
class Dog extends Pet{
private String color;
public Dog(String name, int age, int health) {
// super 超类、父类,调用父类的构造方法
super(name, age, health);
}
public Dog(String name, int age, int health, String color) {
super(name, age, health);
this.color = color;
}
public String getColor() {
return color;
}
public void setColor(String color) {
this.color = color;
}
@Override
public String toString() {
return "Dog{" +
"color='" + color + '\'' +
"} " + super.toString();
}
}
抽象类 abstract
abstract class Animal{
// 抽象方法:只有声明,没有实现(花括号里面那部分)
public abstract void run();
// 普通方法:声明+实现
public void eat(){
System.out.println("Animal is eating...");
}
}
接口 interface
interface Fly{
// public abstract 可以省略
public abstract void fly();
}
// 实现类
class Bird implements Fly{
@Override
public void fly() {
System.out.println("鸟在树林中飞。");
}
}
class Plane implements Fly{
@Override
public void fly() {
System.out.println("飞机在空中飞。");
}
}
关键字 final
final class A {}
//class B extends A {} // 类A不能被继承
class B {
final float PI = 3.14F; // 常量
public static final float pi = 3.14f; // 常量
public final void func(){
final String name;
name = "Hello";
// name = "Hello world"; // 只能被赋值一次
// PI = 3.1415926F;
}
}
静态 static
public static void getCount(){
// 非静态的成员变量,在静态方法中不能使用
System.out.println(/*name + */"当前票数:" + count);
}
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