Use comparable to sort first by 1st field and then second field in Java
In order to sort first by ID and if the Id’s are same then sort by name. Please follow the code
Example
package collections;
import java.util.List;
import java.util.ArrayList;
import java.util.Collections;
class Student implements Comparable<Student> {
int ID;
String name;
char grade;
public Student(int iD, String name, char grade) {
super();
ID = iD;
this.name = name;
this.grade = grade;
}
@Override
public String toString() {
return "Student [ID=" + ID + ", name=" + name + ", grade=" + grade + "]";
}
@Override
public int compareTo(Student o) {
int result = this.ID - o.ID; // Sorting by ID
if (result == 0) { // if both the integer values are same, then sort by name
result = this.name.compareTo(o.name); // comparing strings
}
return result;
}
}
public class StudentSort {
public static void main(String[] args) {
List<Student> stu = new ArrayList<>();
stu.add(new Student(10, "General Motors", 'A'));
stu.add(new Student(100, "Ferrari", 'B'));
stu.add(new Student(5, "Mustang", 'C'));
stu.add(new Student(5, "Ford", 'F'));
System.out.println("Before");
printCollections(stu);
Collections.sort(stu);
System.out.println("After");
printCollections(stu);
}
private static void printCollections(List<Student> stu) {
for (Student s : stu)
System.out.println(s);
}
}
Output
Before Student [ID=10, name=General Motors, grade=A] Student [ID=100, name=Ferrari, grade=B] Student [ID=5, name=Mustang, grade=C] Student [ID=5, name=Ford, grade=F] After Student [ID=5, name=Ford, grade=F] Student [ID=5, name=Mustang, grade=C] Student [ID=10, name=General Motors, grade=A] Student [ID=100, name=Ferrari, grade=B]
