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[];
         arr[]=new Student("张三",);
         arr[]=new Student("李四",);
         arr[]=new Student("王五",);
         for(int i=;i<;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);
         }
         */

     }
 }