个回答

• 缘来是你

  2016-05-30 18:01:39

  public void testAdd(){

  Course cr=new Course("1","c sharp");

  courseToSelect.add(cr);

  Course temp=(Course)courseToSelect.get(0);

  System.out.println("the add test is: "+cr.id+":"+cr.name);

  Course cr1=new Course("2","my sql");

  courseToSelect.add(0, cr1);

  Course temp1=(Course)courseToSelect.get(1);

  System.out.println("the add test is: "+cr1.id+":"+cr1.name);

  Course[] cse={new Course("3","data struct"),new Course("4","orlce")};

  courseToSelect.addAll(Arrays.asList(cse));

  Course temp2=(Course)courseToSelect.get(2);

  Course temp3=(Course)courseToSelect.get(3);

  System.out.println("the add test is: "+temp2.id+":"+temp2.name);

  System.out.println("the add test is: "+temp3.id+":"+temp3.name);

  Course[] cse1={new Course("5","daxue english"),new Course("6","acess")};

  courseToSelect.addAll(3,Arrays.asList(cse1));

  Course temp4=(Course)courseToSelect.get(3);

  Course temp5=(Course)courseToSelect.get(4);

  System.out.println("the add test is: "+temp4.id+":"+temp4.name);

  System.out.println("the add test is: "+temp5.id+":"+temp5.name);

  Course cr2=new Course("1","c sharp");

  courseToSelect.addAll(6,Arrays.asList(cr2));

  Course temp0=(Course)courseToSelect.get(6);

  System.out.println("the add test is: "+cr2.id+":"+cr2.name);

  }

  public static void main(String[] args) {

  // TODO Auto-generated method stub

  setTest st=new setTest();

  st.testAdd();

  st.testForeach();

  stu s=new stu("3","Slince");

  System.out.println("welcome student"+s.name+"select course");

  Scanner shuru=new Scanner(System.in);

  for(int i=0;i<3;i++){

  System.out.println("input course ID");

  String str=shuru.next();

  for(Course cc:st.courseToSelect){

  if(cc.equals(str)){

  s.courses.add(cc);

  }

  }

  }

  st.setTestforeachforset(s);

  }

  代码出错提示部分

  错误提示

  Exception in thread "main" java.lang.NullPointerException

  at studentInfo.setTest.testAdd(setTest.java:21)

  at studentInfo.setTest.main(setTest.java:49)

  
  

  0

• Aioria_

  2016-05-30 00:58:20

  把代码贴上来！

  0