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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;class Person {
   	private String name;	private int age;	private boolean gender;	private int id = num;	private static int num = 0;	public Person() {
   		System.out.println("This is constructor ");	}	public Person(String name, int age, boolean gender) {
   		this.name = name;		this.gender = gender;		this.age = age;	}	public String getName() {
   		return name;	}	public void setName(String name) {
   		this.name = name;	}	public boolean getGender() {
   		return gender;	}	public void setGender(boolean gender) {
   		this.gender = gender;	}	public int getAge() {
   		return age;	}	public void setAge(int age) {
   		this.age = age;	}	public int getId() {
   		return id;	}	public void setId(int id) {
   		this.id = id;	}	{
   		num++;		System.out.println("This is initialization block, id is " + id);	}		@Override	public String toString() {
   		return "Person [name=" + name + ", age=" + age + ", gender=" + gender + ", id=" + id + "]";	}}public class Main {
   	static {
   		System.out.println("This is static initialization block");	}	public static void main(String[] args) {
   		Scanner in = new Scanner(System.in);		int n = in.nextInt();		Person p[] = new Person[n];		for (int i = 0; i < p.length; i++) {
   			String a = in.next();			int b = in.nextInt();			boolean c = in.nextBoolean();			p[i] = new Person(a, b, c);		}		for (int i = n - 1; i >= 0; i--) {
   			System.out.println(p[i]);		}		Person p1 = new Person();		System.out.println(p1.getName() + "," + p1.getAge() + "," + p1.getGender() + "," + p1.getId());		System.out.println(p1);	}}

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