Retrieve attribute using ArrayList?

Question

*import java.util.*;  
public class UserArrayList {
    public static void main(String[] args) {
        //Creating user defined class objects  
        Student s1=new Student(1,"AAA",13);  
        Student s2=new Student(2,"BBB",14);  
        Student s3=new Student(3,"CCC",15); 
        ArrayList<Student> al=new ArayList<Student>();
        al.add(s1);
        al.add(s2);  
        al.add(s3);  
        Iterator itr=al.iterator();  
        //traverse elements of ArrayList object  
        while(itr.hasNext()){  
            Student st=(Student)itr.next();  
            System.out.println(st.rollno+" "+st.name+" "+st.age);  
        }  
    }
}
class Student{  
    int rollno;  
    String name;  
    int age;  
    Student(int rollno,String name,int age){  
        this.rollno=rollno;  
        this.name=name;  
        this.age=age;  
    }  
}

How do I retrieve a single attribute of Student class using ArrayList or check whether "AAA" is present in the list?

If you are using Java 8 you can use : Student find = al.stream() .filter(s -> s.name.equals("AAA")) .findFirst() .orElse(null); — Youcef LAIDANI
– Youcef LAIDANI, Commented Jun 21, 2018 at 12:44
"or check whether "AAA" is present in the list?" This part is easy: in the while-loop you already have, you can use if("AAA".equals(st.name)). I would suggest adding getter and setter methods to your Student-DTO, though. In which case .name becomes .getName(). — Kevin Cruijssen
– Kevin Cruijssen, Commented Jun 21, 2018 at 13:03
You did it in your code acutally. Inside System.out.println you get st.name. All you have to do is just do st.name.equals("AAA"); — Rafał Sokalski
– Rafał Sokalski, Commented Jun 21, 2018 at 13:03

Rafał Sokalski · Accepted Answer · 2018-06-21 13:05:25Z

Just added two lines and btw. you have error in that code when you create ArrayList. You wrote "ArayList" which is wrong.

Method 1.

public static void main(String[] args) {
            //Creating user defined class objects  
            Student s1=new Student(1,"AAA",13);  
            Student s2=new Student(2,"BBB",14);  
            Student s3=new Student(3,"CCC",15); 
            ArrayList<Student> al=new ArrayList<Student>(); // YOU HAVE MISTAKE HERE ArayList<Student>()
            al.add(s1);
            al.add(s2);  
            al.add(s3);  
            Iterator itr=al.iterator();  
            //traverse elements of ArrayList object  
            while(itr.hasNext()){  
                Student st=(Student)itr.next();  
                System.out.println(st.rollno+" "+st.name+" "+st.age);  
                if(st.name.equals("AAA"))  // LINE ADDED
                    System.out.println("present!"); // LINE ADDED

            }  
        }
    }
    class Student{  
        int rollno;  
        String name;  
        int age;  
        Student(int rollno,String name,int age){  
            this.rollno=rollno;  
            this.name=name;  
            this.age=age;  
        }

Method 2 -> Java 8 or higher

  Student find = al.stream().filter(s -> s.name.equals("AAA")).findFirst().orElse(null);
        if(find != null)
            System.out.println("AAA is present");

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