Using TreeMap to sort User-defined Objects in Java
Given example shows how to sort user defined objects TreeMap, you can sort the keys based on the logic provided inside the method.
Given a record of employees name and salary as positive integer, it is required to sort the records on the basis of employee salary, using TreeMap in Java. If salary is same, then use employee name for comparison.
Examples:
Input : xbnnskd 100 geek 50 Output : geek 50 xbnnskd 100 Input : shyam 50 ram 50 Output : ram 50 shyam 50 Explanation : As both the employees have equal pay, sorting is done on the basis of employee's name.
Approach:
1. Traverse through the string and map the employee's salary(S) with the list of employee names having salary S. 2. Use a TreeMap to have keys(Employee's Salary) in a sorted manner. 3. Now, Traverse through the map and print the sorted records.
Below is the implementation of above approach:
// Java program to print employees // records in a sorted manner import java.io.*; import java.util.*; public class GFG { // Function to sort the records static void sortRecords(String records) { // split the string // on the basis of delimiter space(" ") String[] rec = records.split( " " ); // Create a Treemap to store // employee's salary with employee's name Map<Integer, ArrayList<String> > map = new TreeMap<>(); // Traverse the records array // and store values in map for ( int i = 1 ; i < rec.length; i += 2 ) { // Converting String to integer int sal = Integer.parseInt(rec[i]); String name = rec[i - 1 ]; if (map.containsKey(sal)) { ArrayList<String> al = map.get(sal); al.add(name); // Sorting list of employees having Salary sal Collections.sort(al); map.remove(sal); map.put(sal, al); } else { ArrayList<String> al = new ArrayList<>(); al.add(name); map.put(sal, al); } } // Traversing the map // to print the sorted records for (Map.Entry<Integer, ArrayList<String> > entry : map.entrySet()) { ArrayList<String> al1 = entry.getValue(); for ( int i = 0 ; i < al1.size(); i++) System.out.print(al1.get(i) + " " + entry.getKey() + " " ); } } // Driver code public static void main(String args[]) { String records = "Harsh 100 Neha 100 Neha 20 Samay 600 Karan 50" ; // Calling function to sort the records sortRecords(records); } } |
Output:
Neha 20 Karan 50 Harsh 100 Neha 100 Samay 600