5.15 static 应用案例

class Book {
    private String title;
    private static int count = 0;
    public Book(){  // 无参构造
        this("NOTITLE - " + count++);// 避免了没有title的情况，调用下面的构造方法，把“NOTITLE - count”当作title
    }

    public Book(String title){
        this.title = title;
    }

    public String getTitle(){
        return this.title;
    }

}

public class HelloWorld {
    public static void main(String[] args) {
        System.out.println(new Book("Java").getTitle());
        System.out.println(new Book("JSP").getTitle());;
        System.out.println(new Book("Spring").getTitle());
        System.out.println(new Book().getTitle());
        System.out.println(new Book().getTitle());
    }
}