如何将信息添加到arraylist中的现有元素？

Question

have a question about this code. How can I add information to an existing element? For example in the beginning the machine asks the user to give a name. If I give the name "Harry" the machine will just say "the student name is correct" but I want also to see the age of that student and in general some information. So my question is how can I add informations for each student? Here is my code so far. Thanks in advance!

package test;

import java.util.*;

public class readStudents {
    public static void main(String []args) {




        ArrayList<String> arrlstStr = new ArrayList<String>(); //Declaring ArrayList

        arrlstStr.add("Malte");
        arrlstStr.add("Timo");
        arrlstStr.add("Harry");
        arrlstStr.add("Julian");
        arrlstStr.add("Musa");
        arrlstStr.add("Mirnes");
        arrlstStr.add("Daniel");
        arrlstStr.add("David");
        arrlstStr.add("Nico");
        arrlstStr.add("Ranya");
        arrlstStr.add("Xuan");
        arrlstStr.add("Sören");
        arrlstStr.add("Mark");
        arrlstStr.add("Salomon");
        arrlstStr.add("Leon");
        arrlstStr.add("Niklas");
        arrlstStr.add("Tobias");

        System.out.println("Enter the name of the student: ");
        Scanner scanner = new Scanner(System.in);
        String student = scanner.nextLine();

        if (arrlstStr.contains(student)) {
            System.out.println("This student name is correct");
        }
        else { 
            System.out.println("You gave a wrong name");
        }
    }
}

Answer 1

public class Student {
 private String name;
 private int age;

// other fields with getter and setter
}

public class StudentFields {

public static void main(String []args){
 ArrayList<Student> arrlstStr = new ArrayList<Student>(); //Declaring ArrayList
Student s1 = new Student();
s1.setName("R1");
s1.setAge(20);

    arrlstStr.add(s1);
    arrlstStr.add(s2);
}
}

A very simple thing to do :)

Answer 2

You will agree with me that, array list is a collection of list of elements. This elements in your case were pre-defined. What I would suggest is that you have to also define the information you want any element to have. For example; student name 'Harry' should have a piece of corresponding information like age pointing to it; student_age; eg Harry_age set to '34'. something like this:

arrlstStr.add("Harry") ;

arrlstStr.add("Harry_age")

assigning value to the element

Harry_age = 34;

The above illustration is to guide you. Once you have defined that, make you use of your if-statement. The pseudo-code is; IF student name is "Harry" THEN DISPLAY 34 (Harry's age)

This should work. Is just simple logic.

Answer 3

As per your requirement I would recommend to use map instead of Array list and keep the student name as key and student object as value so on bases of name you can get student information.such as below

public class Student {
 private String name;
 private int age;

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

 public String getName() {
    return name;
 }

 public int getAge() {
    return age;
 }

}

public class StudentData {

public static void main(String []args){
Map<String,Student> studentCollection=new HashMap<String,Student>();
Student student = new Student("Sachin",40);
studentCollection.put(student.getName(),student);
.
.


}

}