How to sort a List of Map objects?

Question

I have a List<Map> myList where each map object has a key, called priority , and I would like to sort this list by the priority . I have no idea, how should I manage it.

Answer 1

each map object has a key, called priority

So i guess, the maps keyset contains Strings. Also, if you want to compare the returned value for the priority key, then this object could implement Comparable.

Collections.sort(myList, new Comparator<Map<String,E extends Comparable>>(){

    @Override
    public int compare(Map<String,E extends Comparable> a, Map<String,E extends Comparable> b){
        return a.get("priority").compareTo(b.get("priority"));
        //alternative:
        //if(a.get("priority").equals(b.get("priority"))return 0;
        //if(a.get("priority") > (b.get("priority"))return 1;
        //return -1;
    }
})

Answer 2

public class MyComparator implements Comparator<Map> { public void compare (Map m1, Map m2) { return ((Integer)m1.get("priority")).compareTo(m2.get("priority"))); } } // ... list.sort(new MyComparator());

如果您不使用整数，则将Integer强制转换为另一个Number子类

Answer 3

If using Java8

myList
.stream()
.sorted((obj1, obj2) -> Integer.compare(obj1.get("Priority"), obj2.get("Priority"))
.collect(Collectors.toList())