lesson ten 2018-04-29 14:58:07
super:
1.可以用来修饰属性、方法、构造器
1 public class CheckAccount extends Demo1 {
2
3 public double getOverdraft() {
4 return overdraft;
5 }
6
7 public void setOverdraft(double overdraft) {
8 this.overdraft = overdraft;
9 }
10
11 private double overdraft;
12
13 public CheckAccount(int id, double balance, double annualInterestRate,
14 double overdraft) {
15 super(id, balance, annualInterestRate);
16 this.overdraft = overdraft;
17 }
18
19 public void withdraw(double amount) {
20 if (balance >= amount) {
21 balance -= amount;
22 } else if (overdraft + balance >= amount) {
23 overdraft = overdraft - (amount - balance);
24 balance = 0;
25 } else {
26 System.out.println("透支额度不够");
27 }
28 }
29 }
2.当子类与父类有同名的属性时，可以通过“super.该属性”显式的调用父类中声明的属性。
1 public class Demo1 {
2 private int id;
3 double balance;
4 private double annualInterestRate;
5
6 public Demo1(){
7 System.out.println("这是空参构造器");
8 }
9
10 public Demo1(int id, double balance, double annualInterestRate) {
11 super();
12 this.id = id;
13 this.balance = balance;
14 this.annualInterestRate = annualInterestRate;
15 }
16
17 public int getId() {
18 return id;
19 }
20
21 public void setId(int id) {
22 this.id = id;
23 }
24
25 public double getBalance() {
26 return balance;
27 }
28
29 public void setBalance(double balance) {
30 this.balance = balance;
31 }
32
33 public double getAnnualInterestRate() {
34 return annualInterestRate;
35 }
36
37 public void setAnnualInterestRate(double annualInterestRate) {
38 this.annualInterestRate = annualInterestRate;
39 }
40
41 public double getMonthlyInterest() {//月利率
42 return this.annualInterestRate/12;
43 }
44 //存钱
45 public void deposit(double amount) {
46 this.balance += amount;
47 }
48 //取钱
49 public void withdraw(double amount) {
50 if (this.balance >= amount) {
51 this.balance -= amount;
52 }else {
53 System.out.println("余额不足");
54 }
55 }
56 }
3.当子类重写父类的方法以后，在子类中若想再显式的调用父类的被重写的方法，就需要使用“super.该方法”
super修饰构造器：
1.通过在子类中使用，“super(形参列表)”来显式的调用父类中指定的构造器.
2.在构造器内部，“super(形参列表)”必须要声明在首行！
3.在构造器内部，“super(形参列表)”/“this(形参列表)”只能出现一个
4.当构造器中，不显示调用“super(形参列表)”/“this(形参列表)”其中之一，
5.默认调用父类空参的构造器。
建议：设计一个类时，尽量要提供一个空参
1 public class SubClass { 2 3 public static void main(String[] args) { 4 Dog dog = new Dog("XiaoMing", "DaHuang", 5); 5 } 6 } 7 8 class Creator{ 9 private int age; 10 public int getAge() { 11 return age; 12 } 13 public void setAge(int age) { 14 this.age = age; 15 } 16 17 public Creator(int age){ 18 this.age = age; 19 System.out.println("1"); 20 System.out.println("its age is "+this.age); 21 } 22 } 23 24 class Animal extends Creator{ 25 private String name; 26 public String getName() { 27 return name; 28 } 29 public void setName(String name) { 30 this.name = name; 31 } 32 33 public Animal(String name, int age){ 34 super(age); 35 this.name = name; 36 System.out.println("2"); 37 System.out.println("its name is "+this.name); 38 } 39 } 40 41 class Dog extends Animal{ 42 private String hostName; 43 public String getHostName() { 44 return hostName; 45 } 46 public void setHostName(String hostName) { 47 this.hostName = hostName; 48 } 49 50 public Dog(String hostname,String name, int age){ 51 super(name, age); 52 this.hostName = hostname; 53 System.out.println("3"); 54 System.out.println("Dog belong to "+this.hostName); 55 } 56 }
