13、面向对象进阶(多态、内部类、常用API)
- 面向对象三大特征之三:多态
-
- 内部类
-
- 内部类概述
- 内部类之一:静态内部类[了解]
- 内部类之二:成员内部类[了解]
- 内部类之三:局部内部类[了解]
- 内部类之四:匿名内部类概述[重点]
- 匿名内部类常见使用形式
- 匿名内部类真实使用场景演示
- 常用API
-
- Objects
- StringBuilder
- Math
- System
- BigDecimal
面向对象三大特征之三:多态
![day13-面向对象进阶(多态、内部类、常用API)_第1张图片](http://img.e-com-net.com/image/info8/b100bec7ca8c4cff9fcd8a5610d9b21f.jpg)
package com.itheima.d1_polymorphic;
public class Animal {
public String name = "动物名称";
public void run(){
System.out.println("动物可以跑~~");
}
}
package com.itheima.d1_polymorphic;
public class Dog extends Animal{
public String name = "狗名称";
@Override
public void run() {
System.out.println("跑的贼溜~~~~~");
}
}
package com.itheima.d1_polymorphic;
public class Tortoise extends Animal{
public String name = "乌龟名称";
@Override
public void run() {
System.out.println("跑的非常慢~~~");
}
}
package com.itheima.d1_polymorphic;
public class Test {
public static void main(String[] args) {
Animal a = new Dog();
a.run();
System.out.println(a.name);
Animal a1 = new Dog();
a1.run();
System.out.println(a1.name);
}
}
多态的优势
![day13-面向对象进阶(多态、内部类、常用API)_第2张图片](http://img.e-com-net.com/image/info8/f650fc14c07a467a8f7b841e4918cae3.jpg)
package d2_polymorphic_advantage;
public class Animal {
public String name = "动物名称";
public void run(){
System.out.println("动物可以跑~~");
}
}
package d2_polymorphic_advantage;
public class Dog extends Animal {
public String name = "狗名称";
@Override
public void run() {
System.out.println("跑的贼溜~~~~~");
}
public void lookDoor(){
System.out.println("在看!!!");
}
}
package d2_polymorphic_advantage;
public class Tortoise extends Animal {
public String name = "乌龟名称";
@Override
public void run() {
System.out.println("跑的非常慢~~~");
}
}
package d2_polymorphic_advantage;
public class Test {
public static void main(String[] args) {
Animal d = new Dog();
go(d);
Animal t = new Tortoise();
go(t);
}
public static void go(Animal a){
System.out.println("预备~~~");
a.run();
System.out.println("结束~~~~");
}
}
![day13-面向对象进阶(多态、内部类、常用API)_第3张图片](http://img.e-com-net.com/image/info8/1fe889610e7f4731911346ee7ed39659.jpg)
package d3_polymorphic_convert;
public class Animal {
public String name = "动物名称";
public void run(){
System.out.println("动物可以跑~~");
}
}
package d3_polymorphic_convert;
public class Dog extends Animal {
public String name = "狗名称";
@Override
public void run() {
System.out.println("跑的贼溜~~~~~");
}
public void lookDoor(){
System.out.println("在看!!!");
}
}
package d3_polymorphic_convert;
public class Tortoise extends Animal {
public String name = "乌龟名称";
@Override
public void run() {
System.out.println("跑的非常慢~~~");
}
public void layEggs(){
System.out.println("在下蛋~~~");
}
}
package d3_polymorphic_convert;
public class Test {
public static void main(String[] args) {
Animal a = new Dog();
a.run();
Dog d = (Dog) a;
d.lookDoor();
if(a instanceof Tortoise){
Tortoise t = (Tortoise) a;
t.layEggs();
}else if(a instanceof Dog){
Dog d1 = (Dog) a;
d1.lookDoor();
}
System.out.println("---------------------");
Animal a1 = new Dog();
go(a1);
}
public static void go(Animal a){
System.out.println("预备~~~");
a.run();
if(a instanceof Tortoise){
Tortoise t = (Tortoise) a;
t.layEggs();
}else if(a instanceof Dog){
Dog d1 = (Dog) a;
d1.lookDoor();
}
System.out.println("结束~~~~");
}
}
![day13-面向对象进阶(多态、内部类、常用API)_第4张图片](http://img.e-com-net.com/image/info8/6dee15542af542b995908a5846cc0781.jpg)
多态的案例
![day13-面向对象进阶(多态、内部类、常用API)_第5张图片](http://img.e-com-net.com/image/info8/160ab3a6fcbd40d0bc30a63c4a7dcf59.jpg)
package d4_polymorphic_test;
public class Computer {
public void installUSB(USB u){
u.connect();
if(u instanceof Mouse){
Mouse m = (Mouse) u;
m.click();
}else if(u instanceof KeyBoard) {
KeyBoard k = (KeyBoard) u;
k.keyDown();
}
u.unconnect();
}
}
package d4_polymorphic_test;
public class KeyBoard implements USB{
private String name;
public KeyBoard(String name) {
this.name = name;
}
@Override
public void connect() {
System.out.println(name + "成功的接入了设备了~~~");
}
@Override
public void unconnect() {
System.out.println(name + "成功的从设备弹出了~~~");
}
public void keyDown(){
System.out.println(name + "写下了:老铁,6666,下次再来哦,老弟~~~~");
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
package d4_polymorphic_test;
public class Mouse implements USB{
private String name;
public Mouse(String name) {
this.name = name;
}
@Override
public void connect() {
System.out.println(name + "成功的接入了设备了~~~");
}
@Override
public void unconnect() {
System.out.println(name + "成功的从设备弹出了~~~");
}
public void click(){
System.out.println(name + "双击点亮小红心~~~~");
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
package d4_polymorphic_test;
public interface USB {
void connect();
void unconnect();
}
package d4_polymorphic_test;
public class Test {
public static void main(String[] args) {
Computer c = new Computer();
USB u = new Mouse("罗技鼠标");
c.installUSB(u);
USB k = new KeyBoard("双飞燕键盘");
c.installUSB(k);
}
}
内部类
内部类概述
![day13-面向对象进阶(多态、内部类、常用API)_第6张图片](http://img.e-com-net.com/image/info8/f215ecedfd6b4e3eb0f6a9f8bb8c87ef.jpg)
![day13-面向对象进阶(多态、内部类、常用API)_第7张图片](http://img.e-com-net.com/image/info8/29cae0f0f964492ca507f6af34ce6ac3.jpg)
内部类之一:静态内部类[了解]
![day13-面向对象进阶(多态、内部类、常用API)_第8张图片](http://img.e-com-net.com/image/info8/36f6839b547c4f1181a7f2e31bbe2bdc.jpg)
package d5_innerclass_static;
public class Outer {
public static int a = 100;
private String hobby;
public static class Inner{
private String name;
private int age;
public static String schoolName;
public Inner(){}
public Inner(String name, int age) {
this.name = name;
this.age = age;
}
public void show(){
System.out.println("名称:" + name);
System.out.println(a);
}
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;
}
}
}
package d5_innerclass_static;
public class Test {
public static void main(String[] args) {
Outer.Inner in = new Outer.Inner();
in.setName("张三");
in.show();
}
}
![day13-面向对象进阶(多态、内部类、常用API)_第9张图片](http://img.e-com-net.com/image/info8/4740bdee23474b6dbeb17f6bb1ba7730.jpg)
![day13-面向对象进阶(多态、内部类、常用API)_第10张图片](http://img.e-com-net.com/image/info8/8945df17c2b34f6e8664e580812b16b1.jpg)
![day13-面向对象进阶(多态、内部类、常用API)_第11张图片](http://img.e-com-net.com/image/info8/cf6a3d592d7545a4b2316d043f1eb0be.jpg)
package d6_innerclass;
public class Test2 {
public static void main(String[] args) {
People.Heart heart = new People().new Heart();
heart.show();
}
}
class People{
private int heartbeat = 150;
public class Heart{
private int heartbeat = 110;
public void show(){
int heartbeat = 78;
System.out.println(heartbeat);
System.out.println(this.heartbeat);
System.out.println(People.this.heartbeat);
}
}
}
内部类之二:成员内部类[了解]
![day13-面向对象进阶(多态、内部类、常用API)_第12张图片](http://img.e-com-net.com/image/info8/3715e4f2cd1c4f34a44b871a4996a889.jpg)
package d6_innerclass;
public class Outer {
public static int num = 111;
private String hobby;
public Outer() {
}
public Outer(String hobby) {
this.hobby = hobby;
}
public class Inner{
private String name;
private int age;
public static int a;
System.out.println(a);
}
public void show(){
System.out.println("名称:" + name);
System.out.println("数量:" + num);
System.out.println("爱好:" + hobby);
}
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;
}
}
}
package d6_innerclass;
public class Test {
public static void main(String[] args) {
Outer.Inner in = new Outer().new Inner();
in.setName("内部");
in.show();
System.out.println("------------");
Outer.Inner in1 = new Outer("爱听课").new Inner();
in1.show();
}
}
![day13-面向对象进阶(多态、内部类、常用API)_第13张图片](http://img.e-com-net.com/image/info8/aec563fd9a86428bb827303b4dc20bd7.jpg)
![day13-面向对象进阶(多态、内部类、常用API)_第14张图片](http://img.e-com-net.com/image/info8/e05f418e450c4b949f65183a842d870b.jpg)
内部类之三:局部内部类[了解]
![day13-面向对象进阶(多态、内部类、常用API)_第15张图片](http://img.e-com-net.com/image/info8/f9ecbc6fd9c043fc8e7f91d8d3d23811.jpg)
package d7_innerclass;
public class Test {
static {
class Dog{
}
abstract class Animal{
}
interface SportManInter{
}
}
public static void main(String[] args) {
class Cat{
private String name;
public static int onLineNumber = 100;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
interface SportManInter{
}
Cat c = new Cat();
c.setName("叮当猫~");
System.out.println(c.getName());
}
}
内部类之四:匿名内部类概述[重点]
![day13-面向对象进阶(多态、内部类、常用API)_第16张图片](http://img.e-com-net.com/image/info8/cddb0e9056314e4aa5eef6de875d0f86.jpg)
package d8_innerclass_anonymous;
public class Test {
public static void main(String[] args) {
Animal a = new Animal(){
@Override
public void run() {
System.out.println("老虎跑的块~~~");
}
};
a.run();
}
}
abstract class Animal{
public abstract void run();
}
![day13-面向对象进阶(多态、内部类、常用API)_第17张图片](http://img.e-com-net.com/image/info8/4304248a83504016b17c9182189c98ac.jpg)
匿名内部类常见使用形式
![day13-面向对象进阶(多态、内部类、常用API)_第18张图片](http://img.e-com-net.com/image/info8/9675628857614f2884a2e012336864cf.jpg)
package d8_innerclass_anonymous;
public class Test2 {
public static void main(String[] args) {
Swimming s = new Swimming() {
@Override
public void swim() {
System.out.println("学生快乐的自由泳");
}
};
go(s);
System.out.println("--------------");
Swimming s1 = new Swimming() {
@Override
public void swim() {
System.out.println("老师泳的贼快~~~~~");
}
};
go(s1);
System.out.println("--------------");
go(new Swimming() {
@Override
public void swim() {
System.out.println("运动员的贼快啊~~~~~");
}
});
}
public static void go(Swimming s){
System.out.println("开始。。。");
s.swim();
System.out.println("结束。。。");
}
}
interface Swimming{
void swim();
}
匿名内部类真实使用场景演示
package d8_innerclass_anonymous;
import javax.swing.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
public class Test3 {
public static void main(String[] args) {
JFrame win = new JFrame("登录界面");
JPanel panel = new JPanel();
win.add(panel);
JButton btn = new JButton("登录");
btn.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
JOptionPane.showMessageDialog(win, "点我一下,说明爱我!");
}
});
panel.add(btn);
win.setSize(400, 300);
win.setLocationRelativeTo(null);
win.setVisible(true);
}
}
![day13-面向对象进阶(多态、内部类、常用API)_第19张图片](http://img.e-com-net.com/image/info8/adf1d89aa72e41a29d31865e498112ec.jpg)
常用API
Object
toString方法
![day13-面向对象进阶(多态、内部类、常用API)_第20张图片](http://img.e-com-net.com/image/info8/f6278e7b57374109a8f0ca7653af7296.jpg)
![day13-面向对象进阶(多态、内部类、常用API)_第21张图片](http://img.e-com-net.com/image/info8/46518e24346441919882b6e64ab42a16.jpg)
![day13-面向对象进阶(多态、内部类、常用API)_第22张图片](http://img.e-com-net.com/image/info8/adee22c823d14a3fad412285841faaf1.jpg)
package d9_api_object;
public class Test1 {
public static void main(String[] args) {
Student s = new Student("周雄", '男', 19);
System.out.println(s);
}
}
package d9_api_object;
import java.util.Objects;
public class Student {
private String name;
private char sex;
private int age;
public Student() {
}
public Student(String name, char sex, int age) {
this.name = name;
this.sex = sex;
this.age = age;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public char getSex() {
return sex;
}
public void setSex(char sex) {
this.sex = sex;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
@Override
public boolean equals(Object o) {
if (this == o) return true;
if (o == null || this.getClass() != o.getClass()) return false;
Student student = (Student) o;
return sex == student.sex && age == student.age && Objects.equals(name, student.name);
}
@Override
public String toString() {
return "Student{" +
"name='" + name + '\'' +
", sex=" + sex +
", age=" + age +
'}';
}
}
![day13-面向对象进阶(多态、内部类、常用API)_第23张图片](http://img.e-com-net.com/image/info8/f8c209de69ae49c8b89fc438ac8f92af.jpg)
equals方法
package d9_api_object;
import java.util.Objects;
public class Test2 {
public static void main(String[] args) {
Student s1 = new Student("周雄", '男', 19);
Student s2 = new Student("周雄", '男', 19);
System.out.println(s1.equals(s2));
System.out.println(s1 == s2);
System.out.println(Objects.equals(s1, s2));
}
}
![day13-面向对象进阶(多态、内部类、常用API)_第24张图片](http://img.e-com-net.com/image/info8/1a3c794f941d4584abb5d9a5ec039fb9.jpg)
![day13-面向对象进阶(多态、内部类、常用API)_第25张图片](http://img.e-com-net.com/image/info8/8345293d024646e6a3b5391b42916477.jpg)
Objects
![day13-面向对象进阶(多态、内部类、常用API)_第26张图片](http://img.e-com-net.com/image/info8/8e3a68992ecc489f8367e57723fcd8e1.jpg)
package d10_api_objects;
import java.util.Objects;
public class Test {
public static void main(String[] args) {
String s1 = null;
String s2 = new String("itheima");
System.out.println(Objects.equals(s1, s2));
System.out.println(Objects.isNull(s1));
System.out.println(s1 == null);
System.out.println(Objects.isNull(s2));
System.out.println(s2 == null);
}
}
![day13-面向对象进阶(多态、内部类、常用API)_第27张图片](http://img.e-com-net.com/image/info8/37a2b2ddcf18497d84532df43a486e29.jpg)
![day13-面向对象进阶(多态、内部类、常用API)_第28张图片](http://img.e-com-net.com/image/info8/d8ba2b40f2734f408ddffda257751155.jpg)
StringBuilder
![day13-面向对象进阶(多态、内部类、常用API)_第29张图片](http://img.e-com-net.com/image/info8/8e5277b68445414098522152b6dd121c.jpg)
![day13-面向对象进阶(多态、内部类、常用API)_第30张图片](http://img.e-com-net.com/image/info8/2ae094ee8f8d4effa2dd94e9855fe704.jpg)
package d11_api_stringbuilder;
public class StringBuilderDemo1 {
public static void main(String[] args) {
StringBuilder sb = new StringBuilder();
sb.append("a");
sb.append("b");
sb.append("c");
sb.append(1);
sb.append(false);
sb.append(3.3);
sb.append("abc");
System.out.println(sb);
StringBuilder sb1 = new StringBuilder();
sb1.append("a").append("b").append("c").append("我爱你中国");
System.out.println(sb1);
sb1.reverse().append("110");
System.out.println(sb1);
System.out.println(sb1.length());
StringBuilder sb2 = new StringBuilder();
sb2.append("123").append("456");
String rs = sb2.toString();
check(rs);
}
public static void check(String data){
System.out.println(data);
}
}
![day13-面向对象进阶(多态、内部类、常用API)_第31张图片](http://img.e-com-net.com/image/info8/d654b2864495462094f911de6cfd3b90.jpg)
![day13-面向对象进阶(多态、内部类、常用API)_第32张图片](http://img.e-com-net.com/image/info8/925258ab43924a40950334f825ebbfe0.jpg)
![day13-面向对象进阶(多态、内部类、常用API)_第33张图片](http://img.e-com-net.com/image/info8/0735c3e394924995bcae35f743d5be47.jpg)
![day13-面向对象进阶(多态、内部类、常用API)_第34张图片](http://img.e-com-net.com/image/info8/76e1e487dfe1408aa5faffd093ec5dbb.jpg)
package d11_api_stringbuilder;
public class StringBuilderTest2 {
public static void main(String[] args) {
int[] arr1 = null;
System.out.println(toString(arr1));
int[] arr2 = {10, 88, 99};
System.out.println(toString(arr2));
int[] arr3 = {};
System.out.println(toString(arr3));
}
public static String toString(int[] arr){
if(arr != null){
StringBuilder sb = new StringBuilder("[");
for (int i = 0; i < arr.length; i++) {
sb.append(arr[i] ).append(i == arr.length - 1 ? "" : ", ");
}
sb.append("]");
return sb.toString();
}else {
return null;
}
}
}
Math
![day13-面向对象进阶(多态、内部类、常用API)_第35张图片](http://img.e-com-net.com/image/info8/89ee4c55a987408ca8dadddf78fc660e.jpg)
package d12_math;
public class MathDemo {
public static void main(String[] args) {
System.out.println(Math.abs(10));
System.out.println(Math.abs(-10.3));
System.out.println(Math.ceil(4.00000001));
System.out.println(Math.ceil(4.0));
System.out.println(Math.floor(4.99999999));
System.out.println(Math.floor(4.0));
System.out.println(Math.pow(2 , 3));
System.out.println(Math.round(4.49999));
System.out.println(Math.round(4.500001));
System.out.println(Math.random());
int data = (int)(Math.random() * 7) + 3;
System.out.println(data);
}
}
System
![day13-面向对象进阶(多态、内部类、常用API)_第36张图片](http://img.e-com-net.com/image/info8/633734167b854056b5b06f9f280e79cf.jpg)
![day13-面向对象进阶(多态、内部类、常用API)_第37张图片](http://img.e-com-net.com/image/info8/db43f8d0cbb44d3992b225e087e63b59.jpg)
package d13_system;
import java.math.BigDecimal;
import java.math.RoundingMode;
import java.text.SimpleDateFormat;
import java.util.Arrays;
public class SystemDemo {
public static void main(String[] args) {
System.out.println("程序开始。。。");
long time = System.currentTimeMillis();
System.out.println(time);
long startTime = System.currentTimeMillis();
for (int i = 0; i < 100000; i++) {
System.out.println("输出:" + i);
}
long endTime = System.currentTimeMillis();
System.out.println((endTime - startTime)/1000.0 + "s");
int[] arr1 = {10, 20, 30, 40, 50, 60, 70};
int[] arr2 = new int[6];
System.arraycopy(arr1, 3, arr2, 2, 3);
System.out.println(Arrays.toString(arr2));
System.out.println("-------------------");
double i = 10.0;
double j = 3.0;
System.out.println("程序结束。。。。");
}
}
BigDecimal
![day13-面向对象进阶(多态、内部类、常用API)_第38张图片](http://img.e-com-net.com/image/info8/9a914a3570f6468cb9d89c93e904c1ae.jpg)
![day13-面向对象进阶(多态、内部类、常用API)_第39张图片](http://img.e-com-net.com/image/info8/a68df2e70c454bdc9bc1c736d65dcaba.jpg)
package d14_bigdecimal;
import java.math.BigDecimal;
import java.math.RoundingMode;
import java.text.NumberFormat;
public class BigDecimalDemo {
public static void main(String[] args) {
System.out.println(0.09 + 0.01);
System.out.println(1.0 - 0.32);
System.out.println(1.015 * 100);
System.out.println(1.301 / 100);
System.out.println("-------------------------");
double a = 0.1;
double b = 0.2;
double c = a + b;
System.out.println(c);
System.out.println("--------------------------");
BigDecimal a1 = BigDecimal.valueOf(a);
BigDecimal b1 = BigDecimal.valueOf(b);
BigDecimal c1 = a1.add(b1);
System.out.println(c1);
double rs = c1.doubleValue();
System.out.println(rs);
BigDecimal a11 = BigDecimal.valueOf(10.0);
BigDecimal b11 = BigDecimal.valueOf(3.0);
BigDecimal c11 = a11.divide(b11, 2, RoundingMode.HALF_UP);
System.out.println(c11);
System.out.println("-------------------");
}
}
![day13-面向对象进阶(多态、内部类、常用API)_第40张图片](http://img.e-com-net.com/image/info8/b677490366f449d9ab83a8b5feb1a219.jpg)
![day13-面向对象进阶(多态、内部类、常用API)_第41张图片](http://img.e-com-net.com/image/info8/d48aa10d621b41b9b20aebc0ec5d06ad.jpg)