SortedMap
In this chapter you will learn:
- How to use SortedMap
- How to get first key from SortedMap
- How to get last key and last key value pair in SortedMap
Use SortedMap
SortedMap is a map that maintains its entries in ascending order.
Sorted Map sorts the entries according to the keys' natural ordering or according
to a comparator that is supplied when the sorted map is created.
Sorted maps are described by the SortedMap interface.
TreeMap is an example of a sorted map.
SortedMap, whose generic type is SortedMap<K,V>, extends Map.
import java.util.Comparator;
import java.util.SortedMap;
import java.util.TreeMap;
/*from ja v a 2 s .com*/
public class Main {
public static void main(String[] args) {
SortedMap<String, Integer> sortedMap = new TreeMap<String, Integer>();
String[] officeSupplies = { "a", "b", "c", "d", "e" };
int[] quantities = { 20, 30, 5, 10, 20 };
for (int i = 0; i < officeSupplies.length; i++){
sortedMap.put(officeSupplies[i], quantities[i]);
}
System.out.println(sortedMap);
System.out.println(sortedMap.headMap("c"));
System.out.println(sortedMap.headMap("c"));
SortedMap<String, Integer> smsiCopy;
Comparator<String> cmp;
cmp = new Comparator<String>() {
public int compare(String key1, String key2) {
return key2.compareTo(key1); // descending order
}
};
smsiCopy = new TreeMap<String, Integer>(cmp);
smsiCopy.putAll(sortedMap);
System.out.println(smsiCopy);
}
}
The output:
Get first key from SortedMap
import java.util.Calendar;
import java.util.Locale;
import java.util.Map;
import java.util.NavigableMap;
import java.util.TreeMap;
//from jav a 2 s . com
public class Main {
public static void main(String args[]) {
Calendar now = Calendar.getInstance();
Locale locale = Locale.getDefault();
Map<String, Integer> names = now.getDisplayNames(Calendar.DAY_OF_WEEK, Calendar.LONG, locale);
NavigableMap<String, Integer> nav = new TreeMap<String, Integer>(names);
System.out.printf("Whole list:%n%s%n", nav);
System.out.printf("First key: %s\tFirst entry: %s%n", nav.firstKey(), nav.firstEntry());
}
}
The code above generates the following result.
Last key and last key value pair in SortedMap
import java.util.Calendar;
import java.util.Locale;
import java.util.Map;
import java.util.NavigableMap;
import java.util.TreeMap;
// jav a 2 s . c o m
public class Main {
public static void main(String args[]) {
Calendar now = Calendar.getInstance();
Locale locale = Locale.getDefault();
Map<String, Integer> names = now.getDisplayNames(Calendar.DAY_OF_WEEK, Calendar.LONG, locale);
NavigableMap<String, Integer> nav = new TreeMap<String, Integer>(names);
System.out.printf("Whole list:%n%s%n", nav);
System.out.printf("Last key: %s\tLast entry: %s%n", nav.lastKey(), nav.lastEntry());
}
}
The code above generates the following result.
Next chapter...
What you will learn in the next chapter:
Home » Java Tutorial » Map