Discussion on java sorting and TreeSet sorting
- 2020-05-19 04:56:07
- OfStack
TreeMap:
package com;
import java.util.Comparator;
import java.util.TreeMap;
public class Test5 {
/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
TreeMap<String, String> tree = new TreeMap<String, String>(
new Comparator<Object>() {
@Override
public int compare(Object o1, Object o2) {
// TODO Auto-generated method stub
if(o1 == null || o2 == null){
return 0;
}
return o1.toString().compareTo(o2.toString());
}
}
);
tree.put("k", "1");
tree.put("ba", "2");
tree.put("z", "3");
tree.put("d", "4");
tree.put("e", "5");
tree.put("an", "6");
tree.put("c", "7");
for(String str : tree.keySet()){
System.out.println(str);
}
}
}
The default is KEY by default.
You can, however, write object comparators for custom sorting.
TreeSet: custom reverse sort, default sort in positive order, 1,2,3,4,5,6
package com;
import java.util.Comparator;
import java.util.TreeSet;
public class Test6 {
/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
TreeSet<Object> tree = new TreeSet<Object>(new Comparator<Object>() {
@Override
public int compare(Object o1, Object o2) {
// TODO Auto-generated method stub
if(o1 == null || o2 == null){
return 0;
}
if(Integer.parseInt(o1.toString()) > Integer.parseInt(o2.toString())){
return -1;
}else if(Integer.parseInt(o1.toString()) < Integer.parseInt(o2.toString())){
return 1;
}else{
return 0;
}
}
});
tree.add(4);
tree.add(5);
tree.add(6);
tree.add(1);
tree.add(2);
tree.add(3);
for(Object o : tree){
System.out.println(o);
}
}
}