构造函数 - Cirry's Blog

构造方法的定义

构造方法名称必须与类名称保持一致。
构造方法不允许设置任何的返回值类型，即：没有返回值定义。
构造方法是在使用关键字new实例化对象的时候自动调用的。
简单类的定义方法

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class Person{
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    private String name;
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    private int age;
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    public Person(){
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        this("dog",18);
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    }
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    public  Person(String name){
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        this(name, 28);
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    }
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    public  Person(String name, int age){
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        this.name = name;
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        this.age = age;
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    }
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    public void getInfo (){
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        System.out.println("my name is "+this.name+",my age is "+this.age) ;
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    }
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    public void setName(String name){
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        this.name = name;
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    }
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    public void setAge(int age){
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        this.age = age;
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    }
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    public String getName(){
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        return this.name;
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    }
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    public Number getAge(){
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        return this.age;
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    }
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}
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public class JavaDemo {
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    public static void main( String args []){
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        Person per = new Person("ccc",25);
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        per.getInfo();
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    }
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}

带静态变量static的类构造

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class Book{
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    private String name;
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    private int bid ;
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    private double price ;
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    private static int count = 0;
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    public Book(){
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    }
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    public Book(String name , double price){
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        this.bid = count++;
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        this.name = name;
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        this.price = price;
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    }
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    public String getInfo(){
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        return "book name:"+this.name+",book price:"+this.price;
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    }
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    public static int getCount (){
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        return count;
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    }
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}
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public class JavaDemo {
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    public static void main(String args []){
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        Book b3 = new Book("html", 100.00);
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        Book b2 = new Book("html2", 222200.00);
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        System.out.println(b3.getInfo());
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        System.out.println(Book.getCount());
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    }
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}

简单类的练习

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class User{
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    private String name;
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    private int no;
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    public User(String name , int no){
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        this.name = name;
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        this.no = no;
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    }
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    public void setName(String name ){
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        this.name = name;
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    }
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    public void setNo (int no ){
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        this.no = no;
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    }
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    public String getName (){
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        return this.name;
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    }
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    public int getNo(){
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        return this.no;
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    }
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    public String getInfo(){
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        return "my name is "+ this.name+",my no is "+this.no;
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    }
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}
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public class Demo {
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    public static void main(String args []){
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        User user1 = new User("cirry", 1);
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        User user2 = new User("winnie", 2);
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        System.out.println(user1.getInfo());
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        System.out.println(user2.getInfo());
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        user1.setName("cirry666");
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        System.out.println(user1.getNo());
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        System.out.println(user1.getInfo());
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        user2.setNo(2);
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        System.out.println(user2.getInfo());
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    }
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}