How to use SortedMap interface in Java?
TreeMap, which is an implementation of the SortedMap interface, would work.
How do I use it ?
Map<Float, MyObject> map = new TreeMap<Float, MyObject>();
I would use TreeMap
, which implements SortedMap
. It is designed exactly for that.
Example:
Map<Integer, String> map = new TreeMap<Integer, String>();
// Add Items to the TreeMap
map.put(1, "One");
map.put(2, "Two");
map.put(3, "Three");
// Iterate over them
for (Map.Entry<Integer, String> entry : map.entrySet()) {
System.out.println(entry.getKey() + " => " + entry.getValue());
}
See the Java tutorial page for SortedMap.
And here a list of tutorials related to TreeMap.
A TreeMap is probably the most straightforward way of doing this. You use it exactly like a normal Map. i.e.
Map<Float,String> mySortedMap = new TreeMap<Float,MyObject>();
// Put some values in it
mySortedMap.put(1.0f,"One");
mySortedMap.put(0.0f,"Zero");
mySortedMap.put(3.0f,"Three");
// Iterate through it and it'll be in order!
for(Map.Entry<Float,String> entry : mySortedMap.entrySet()) {
System.out.println(entry.getValue());
} // outputs Zero One Three
It's worth taking a look at the API docs, http://download.oracle.com/javase/6/docs/api/java/util/TreeMap.html to see what else you can do with it.
You can use TreeMap which internally implements the SortedMap below is the example
Sorting by ascending ordering :
Map<Float, String> ascsortedMAP = new TreeMap<Float, String>();
ascsortedMAP.put(8f, "name8");
ascsortedMAP.put(5f, "name5");
ascsortedMAP.put(15f, "name15");
ascsortedMAP.put(35f, "name35");
ascsortedMAP.put(44f, "name44");
ascsortedMAP.put(7f, "name7");
ascsortedMAP.put(6f, "name6");
for (Entry<Float, String> mapData : ascsortedMAP.entrySet()) {
System.out.println("Key : " + mapData.getKey() + "Value : " + mapData.getValue());
}
Sorting by descending ordering :
If you always want this create the map to use descending order in general, if you only need it once create a TreeMap with descending order and put all the data from the original map in.
// Create the map and provide the comparator as a argument
Map<Float, String> dscsortedMAP = new TreeMap<Float, String>(new Comparator<Float>() {
@Override
public int compare(Float o1, Float o2) {
return o2.compareTo(o1);
}
});
dscsortedMAP.putAll(ascsortedMAP);
for further information about SortedMAP read http://examples.javacodegeeks.com/core-java/util/treemap/java-sorted-map-example/