1.类，方法，对象，构造函数的例题（1）
public class Account {
//private 只在本类中运行。
//public在所有的工程中都可以调用。
//protected只在本类本包和子类中调用。 //实例方法如果是public类型则所有可运行。
//default在本来和子类中被调用。
//get有返回值但是没有参数，set没有返回值但是有参数。
private String id;
private String name;
private int balance = 0;
public Account(String id, String name) {
this.id = id;
this.name = name;
}
public Account(String id, String name, int balance) {
this.id = id;
this.name = name;
this.balance = balance;
}
public String getID() {
return id;
}
public String getName() {
return name;
}
public int getbalance() {
return balance;
}
public int credit(int amount) {
balance=balance+amount;
return balance;
}
public int debit(int amount) {
if (amount <= balance) {
balance=balance -amount;
} else {
System.out.println("Amount exceeded balance");
}
return balance;
}
public int transferto(Account another, int amount) {
if (amount <= balance) {
balance =balance-amount;
another.credit(amount);
} else {
System.out.println("Amount exceeded balance");
}
return balance;
}
public String toString() {
return "Account=[id=" + id + ",name=" + name + ",balance=" + balance + ",]";
}
public static void main(String[] args) {
// TODO Auto-generated method stub
Account ac = new Account("2014", "xy",5000); // new是一个关键字，new 的时候就调用了构造函数
ac.credit(5000);
System.out.println(ac.toString()); // 调用函数时，格式要一致。看调用的方法是否有参数，有则需传入对应的参数类型。
}//Account=[id=2014,name=xy,balance=10000,]
}
1.类，方法，对象，构造函数的例题（2）//类的包含。
public class Book{
private String name;
private Author author;
private double price;
private int qty=0;
public Book(String name,Author author,double price){
this.name=name;
this.author=author; //通过构造函数构造了一个实例对象，故在后面再本来中可以直接调用
this.price=price;
}
public Book(String name,Author author,double price,int qty){
this.name=name;
this.author=author;
this.qty=qty;
}
public String getName(){
return name;
}
public Author getAuthor(){
return author;
}
public double getPrice(){
return qty;
}
public void setPrice(double price){
this.price=price;
}
public int getQty(){
return qty;
}
public void setQty(int qty){
this.qty=qty;
}
public String toString(){
String i="Book{name="+name+",email="+author.getEmail()+",gender="+author.getGender()+",price="+price+",qty="+qty+"]";
return i;
}
}
public class Book{
private String name;
private Author author;
private double price;
private int qty=0;
public Book(String name,Author author,double price){
this.name=name;
this.author=author;
this.price=price;
}
public Book(String name,Author author,double price,int qty){
this.name=name;
this.author=author;
this.qty=qty;
}
public String getName(){
return name;
}
public Author getAuthor(){
return author;
}
public double getPrice(){
return qty;
}
public void setPrice(double price){
this.price=price;
}
public int getQty(){
return qty;
}
public void setQty(int qty){
this.qty=qty;
}
public String toString(){
String i="Book{name="+name+",email="+author.getEmail()+",gender="+author.getGender()+",price="+price+",qty="+qty+"]";
return i;}}
public class Book_Test {
public static void main(String[] args) {
Author au = new Author(); //在输出之前需要实例化Author，才能调用。
Book bk = new Book("xiaoyang",au,2000);
System.out.println(bk.toString());}}
1.类，方法，对象，构造函数的例题（3）--将author变成数组。
authors:Author[];
Book[name=xy,author={Author[name=聪哥,email=1@qq.com,gender=女],Author[name=周嘉宇,email=113@qq.com,gender=男]},price=2000.0,qty=0] //输出结果
Book[name=xy,author={},price=2000.0,qty=0] //book.toString()中输出的内容。
Author[name=周嘉宇,email=113@qq.com,gender=男] //Author.toString()中输出的内容。
main 方法中：
Author[] au = {new Author("李聪聪","1015612131@qq.com",'女'),new Author("周嘉宇","11351313@qq.com",'男')}; ——>Author[] au = {new Book(), new Author() };
Book bk = new Book("xiaoyang",au,2000);
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