Using iterator to manipulate complicated objects in ArrayList?

Question

I successfully sort students by id using comparator and displayed using for loop, I hope to know how can I make it happen with iterator, well I tried but only address in console and have no idea of how to print info from Student class

public static void main(String[] args) {
    Student stu1 = new Student("Lucy",1000,99);
    Student stu2 = new Student("Jack",1001,22);
    Student stu3 = new Student("Peter",1002,53);

    ArrayList<Student> student = new ArrayList<Student>();
    student.add(stu1);
    student.add(stu2);
    student.add(stu3);

    Collections.sort(student,new StuCOmp("id"));
    for (int i=0; i<student.size(); i++) {
        Student stu = student.get(i);
        System.out.println(stu.getName() + " "+stu.getId()+ " "+stu.getGrade());    
    }

    Iterator<Student> it = student.iterator();
    while(it.hasNext()){

        //what do I write here
    }
}

Iterator doesn't have many methods. Have you checked uits javadoc? docs.oracle.com/javase/7/docs/api/java/util/Iterator.html — JB Nizet
– JB Nizet, Commented Jul 8, 2014 at 10:06
You basically do the same thing as you would do with a normal for loop. Assign it.next() to temp variable, do whatever, repeat. — awksp
– awksp, Commented Jul 8, 2014 at 10:06

Ninad Pingale · Accepted Answer · 2014-07-08 10:06:52Z

1

You can iterate it like this in for loop -

       for (Iterator<Student> iterator = student.iterator(); iterator.hasNext();) {
            Student stu = iterator.next();
            System.out.println(stu.getName() + " "+stu.getId()+ " "+stu.getGrade());
        }

answered Jul 8, 2014 at 10:06

Ninad Pingale

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3 Comments

JB Nizet Over a year ago

You shouldn't use a raw Iterator. Use an Iterator<Student>

Ninad Pingale Over a year ago

@Suresh:Thanks, once Iterator<Student> is used, no need to caste.

Suresh Atta Over a year ago

@JavaLearner Yes. Now it seems ok. +1.

dips · Accepted Answer · 2014-07-08 10:09:54Z

1

Iterator<Student> it = student.iterator();
    while(it.hasNext()){
        // You should write here:   
        Student stu = it.next();
        System.out.println(stu.getName() + " "+stu.getId()+ " "+stu.getGrade());
     }

answered Jul 8, 2014 at 10:09

dips

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Comments

saurabh kumar · Accepted Answer · 2014-07-08 10:13:05Z

1

Iterator itr=student.iterator();  
  while(itr.hasNext()){  
    Student stu=(Student)itr.next();  
    System.out.println(stu.getName() + " "+stu.getId()+ " "+stu.getGrade());

edited Jul 8, 2014 at 10:13

answered Jul 8, 2014 at 10:07

saurabh kumar

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1 Comment

AJJ Over a year ago

the sys out prints the object means as hash code of object student will be printed. No use of it.

Stelium · Accepted Answer · 2014-07-08 10:23:08Z

1

You can avoid using an iterator and use an enhanced for loop.

for (Student st : student)
    System.out.println(st.getName() + " "+st.getId()+ " "+st.getGrade());

answered Jul 8, 2014 at 10:23

Stelium

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Comments

Ruchira Gayan Ranaweera · Accepted Answer · 2014-07-08 10:20:44Z

0

You can do something like this

Iterator<Student> it = student.iterator();
while(it.hasNext()){
  Student student=it.next();// you can get the students one by one  
  // Now you can get the each student info
  //student.any attribute
}

This way is very similar to for-each but iterator is faster than that.

edited Jul 8, 2014 at 10:20

answered Jul 8, 2014 at 10:14

Ruchira Gayan Ranaweera

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Comments

sdvadsa · Accepted Answer · 2014-07-12 18:06:02Z

0

Iterator itr=student.iterator();  
  while(itr.hasNext()){  
    Student stu=(Student)itr.next();  
    System.out.println("whatever you want to print");

answered Jul 12, 2014 at 18:06

sdvadsa

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