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  • Priority: Medium
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Java Collections sort by name - syntax error

Hi experts,

I have a problem using List, Collections.sort() <== got a syntax error

I have a List of data like below:

         SchoolContactInfo schoolContactInfo [] = {
                  new ArtStudent("Paul", "987654561"),
                  new ArtStudent("Avie", "987654561"),
                  new MathsStudent("John","98769832")};

         List<SchoolContactInfo > mylist = new ArrayList<SchoolContactInfo >();
         mylist.add(schoolContactInfo [0]);
         mylist.add(schoolContactInfo [1]);
         mylist.add(schoolContactInfo [2]);

                    Collections.sort(mylist);

What I want the output sorted by name using Collections sort but i got sysntax saying

SchoolContactInfo is not valid substitute of bounded parameters

My other class like below:

public abstract class SchoolContactInfo {
      private String name;
      private String phone;

      // Constructor
      public ContactInfo(String Name, String Phone) {
            name = Name;
            phone = Phone;
      }

      public String getName() {
            return name;
      }

      public void setName(String name) {
            this.name = name;
      }

      public String getPhone() {
            return phone;
      }

      public void setPhone(String phone) {
            this.phone = phone;
      }
}

public class ArtStudent extends SchoolContactInfo {
      // constructor
      public FriendA(String name, String phone) {
            super(name, phone);
      }
}

public class MathsStudent extends SchoolContactInfo {
      // constructor
      public FriendA(String name, String phone) {
            super(name, phone);
      }
}

===
please correct my syntax. notes i want the output of student sorted by the name
0
unistudent
Asked:
unistudent
  • 3
1 Solution
 
for_yanCommented:
You class
SchoolContactInfo

should implement Comparabale interface
0
 
for_yanCommented:
this compiles without any error:

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

public class School {

    public static void main(String[] args) {

          SchoolContactInfo schoolContactInfo [] = {
                  new ArtStudent("Paul", "987654561"),
                  new ArtStudent("Avie", "987654561"),
                  new MathsStudent("John","98769832")};

         ArrayList<SchoolContactInfo > mylist = new ArrayList<SchoolContactInfo >();
         mylist.add(schoolContactInfo [0]);
         mylist.add(schoolContactInfo [1]);
         mylist.add(schoolContactInfo [2]);

                    Collections.sort(mylist);

        
    }


}


  abstract class SchoolContactInfo implements Comparable <SchoolContactInfo>{
      private String name;
      private String phone;

      // Constructor
      public SchoolContactInfo(String Name, String Phone) {
            name = Name;
            phone = Phone;
      }

      public String getName() {
            return name;
      }

      public void setName(String name) {
            this.name = name;
      }

      public String getPhone() {
            return phone;
      }

      public void setPhone(String phone) {
            this.phone = phone;
      }
      
     public  int compareTo(SchoolContactInfo s){
         
         return s.getName().compareTo(name);
          
      }
}

 class ArtStudent extends SchoolContactInfo {
      // constructor
      public ArtStudent(String name, String phone) {
            super(name, phone);
      }
}

 class MathsStudent extends SchoolContactInfo {
      // constructor
      public MathsStudent(String name, String phone) {
            super(name, phone);
      }
}

Open in new window

0
 
for_yanCommented:
You also hneed to keep in mind that if you define constructor - it should have the same name as the class:

public class ArtStudent extends SchoolContactInfo {
      // constructor
      public FriendA(String name, String phone) {
            super(name, phone);
      }
}

Open in new window


this acuses erroer as you "contructor" has name FriendA ()
different form the name of the class ArtStudent - this causes compilatuion error - i corrected this in the code above
0
 
unistudentAuthor Commented:
so clear. excellent. i am glad he helps me.
0

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