Java中static用来计数

搓搓的代码

import java.util.ArrayList;
import java.util.Iterator;
class Student{
    private static int num;
    private String name;
    private int age;
    private int number;
    public Student(){}
    public Student(String name,int age) {
        num++;
        this.number=num;
        this.name=name;
        this.age=age;
    }
    public void setName(String name) {
        this.name=name;
    }
    public String getName() {
        return name;
    }
    public void setAge(int age) {
        this.age=age;
    }
    public int getAge() {
        return age;
    }
    public int getNumber() {
        return number;
    }
}
public class Main{
    public static void main(String[] args) {
        Student[] arr=new Student[5];
        arr[0]=new Student("张三",19);
        arr[1]=new Student("李四",18);
        arr[2]=new Student("王五",18);
        for(int i=0;i<3;i++) {
            System.out.println(arr[i].getName()+" "+arr[i].getAge()+" "+arr[i].getNumber());
        }
        /*
        ArrayList<String> t =new ArrayList<String>();
        t.add("abc");
        t.add("1551");
        Iterator<String> it = t.iterator();
        while(it.hasNext()) {
             Object obj=it.next();
             System.out.println(obj);
         }
        */
        /*
        ArrayList list = new ArrayList();
        list.add("str");
        list.add(123);
        Iterator it =list.iterator();
        while(it.hasNext()) {
            Object obj=it.next();
            System.out.println(obj);
        }
        */
        
        
    }
}