构造方法与初始化块

1.定义一个Person类
属性：name(String)、gender（boolean)、age(int)、id(int) ，所有的变量必须为私有(private)。
无参构造函数:Person(), 功能：打印This is constructor 。
有参构造函数:Person(name, gender, age) ，功能：给属性赋值。
建议：使用Eclipse自动生成toString方法

2.定义类的初始化块
为Person类加入初始化块，在初始化块中对id属性赋值，并且要保证每次的值比上次创建的对象
的值+1。然后在下一行打印This is initialization block, id is … 其中…是id的值。
提示：可为Person类定义一个static属性来记录所创建的对象个数。

3.编写静态初始化块
打印This is static initialization block

4.编写main方法
首先输入n，代表要创建的对象数量。
然后从控制台分别读取n行的name, gender, age, 并调用有参构造函数Person(name, age, gender)新建对象 。
将创建好的n个对象逆序输出(即输出toString()方法)。
使用无参构造函数新建一个Person对象，然后直接打印该对象。
思考
初始化类与对象有几种方法，构造函数、初始化块、静态初始化块。这三种方法执行的先后顺序是什么？各执行几次。

输入样例:
3
a 11 false
b 12 true
c 10 false
输出样例:
This is static initialization block
This is initialization block, id is 0
This is initialization block, id is 1
This is initialization block, id is 2
Person [name=c, age=10, gender=false, id=2]
Person [name=b, age=12, gender=true, id=1]
Person [name=a, age=11, gender=false, id=0]
This is initialization block, id is 3
This is constructor
null,0,false,3
Person [name=null, age=0, gender=false, id=3]
import java.util.Scanner;
import java.util.Stack;

class Person{
static {
System.out.println(“This is static initialization block”);
}
private String name=null;
private boolean gender=false;
private int age=0;
private int id;
private static int num=0;

public Person(String name, boolean gender, int age) {
    this.name = name;
    this.gender = gender;
    this.age = age;
    id=num;
    num++;
}

public Person() {
    System.out.println("This is initialization block, id is "+num);
    System.out.println("This is constructor");
    id=num;
    num++;
    System.out.println(name+","+age+","+gender+","+id);
    System.out.println(toString());
}

@Override
public String toString() {
    return "Person [" +
            "name=" + name  +
            ", age=" + age +
            ", gender=" + gender +
            ", id=" + id +
            ']';
}
public static int getNum(){
    return num;
}

}
public class Main {
public static void main(String[] args) {
Scanner sc=new Scanner(System.in);
int time=sc.nextInt();
Stack stack=new Stack();
for (int i=0;i String name=sc.next();
int age=Integer.valueOf(sc.next());
boolean gender=Boolean.valueOf(sc.next());
Person p=new Person(name,gender,age);
System.out.println("This is initialization block, id is "+i);
stack.push§;
}
for (int i=0;i Person person=(Person) stack.peek();
System.out.println(person);
stack.pop();
}
new Person();

}

}