int[] arr = new int[10];
int i = arr[-1];
public class TestNull {
public static void main(String[] args) {
Student stu = new Student(1,"a","b");
Teacher tea = new Teacher();
tea.setId(1);
tea.setName("bbb");
tea.setStu(stu);
stu = null;//<span style="color: #FF0000;">這裏可以優化內存麽</span>
System.out.println(tea.getStu().toString());
System.out.println(tea.toString());//
}
}