publicclassCat{//属性String ni_chen; String color;doubleweight;//构造方法publicCat(String ni_chen, String color,doubleweight){ System.out.println("构造方法1被执行");this.ni_chen=ni_chen;this.color=color;this.weight=weight; System.out.println(this.ni_chen+"\t"+this.color+"\t"+this.weig...
}classBook{ String title;intpubYear;staticintcount=0;publicBook(String title){this(title, -1);//如果没有接收到第二个变量,pubYear自动设为1}publicBook(String title,intpubYear){ setTitle(title); setPubYear(pubYear); ++count; }publicvoidsetTitle(String title){this.title = title; }publicvoid...
理解Java的Class类、"this."关键字、Constructor构造器(一),```importjava.util.*;publicclassBookTest{publicstaticvoidmain(String[]args){//Bookbook=newBook("ATaleofTwoCities",1895);Bookbook=newBook("ATaleofTwoCities");Sy...
//构造器 public class ConstructorDemo { public static void main(String[] args) { //调用构造器创建User类的实例对象 //User user = new User();//报错 :The constructor User() is undefined //注意:如果在编写类的时候给出了构造器,那么系统就不会在提供默认构造器,如果还想使用无参构造器,可以自己添加...
class Demo { var id: Long? = null var name: String? = null var age: Int? = null constructor(){} constructor(id: Long) { this.id = id } constructor(name: String, age: Int) { this.name = name this.age = age } } var aa = Demo() ...
简单的说：class 指的是一个类，类代表一个类型的东西。class可以通过constructor（构造方法）来实例一个...
调用实例的print方法，此this是Child的实例，即s=new Child()，Child的print方法是打印的child，所以输出...
在上述代码中，由于调用语句this()不是构造方法的第一条执行语句，所以Eclipse在编译时会报出“Constructor call must be the first statement in a constructor（调用构造函数必须是构造函数中的第一条语句）”的错误提示信息。③不能在一个类的两个构造方法中使用this互相调用。下面的写法是错误的：class Person {...
packagecc;publicclassSubextendsSuper{publicSub(String s){}publicstaticvoidmain(String[]args){Sub sub=newSub();}}classSuper{String s;publicSuper(String s){this.s=s;}} 上面这段代码会报错: Implicit super constructor Super() is undefined. Must explicitly invoke another constructor。
Constructs a new throwable with the specified cause and a detail message of (cause==null ? null : cause.toString()) (which typically contains the class and detail message of cause). This constructor is useful for throwables that are little more than wrappers for other throwables (for example...