Sort an ArrayList by primitive boolean type

问题

I want to sort my ArrayList using a boolean type. Basically i want to show entries with true first. Here is my code below:

Abc.java

public class Abc {
 int id;
 bool isClickable;

 Abc(int i, boolean isCl){
    this.id = i;
    this.isClickable = iCl;
 }
 }

Main.java

List<Abc> abc = new ArrayList<Abc>();

//add entries here

//now sort them
Collections.sort(abc, new Comparator<Abc>(){
        @Override
        public int compare(Abc abc1, Abc abc2){

            boolean b1 = abc1.isClickable;
            boolean b2 = abc2.isClickable;

            if (b1 == !b2){
                return 1;
            }
            if (!b1 == b2){
                return -1;
            }
            return 0;
        }
    });

Order before sorting: true true true false false false false true false false

Order after sorting: false false true true true true false false false false

回答1:

Another way to go is:

Collections.sort(abc, new Comparator<Abc>() {
        @Override
        public int compare(Abc abc1, Abc abc2) {
            return Boolean.compare(abc2.isClickable,abc1.isClickable);
        }
    });

回答2:

In this case one of the easiest solutions is to convert booleans to integers, where false is 0 and true is 1. Then return the difference of the second one and the first one.

So:

        int b1 = abc1.isClickable ? 1 : 0;
        int b2 = abc2.isClickable ? 1 : 0;

        return b2 - b1

should do it.

回答3:

why dont use something like this, its easier and java 8

listOfABCElements = {true, false, false, true, true};
listOfABCElements.stream().sorted(Comparator.comparing(Abc::isClickable,Comparator.reverseOrder()).collect(Collectors.toList());

output: true,true,true,false,false

reverseOrder is for order first true and after false, in other case falses goes first

listOfABCElements.stream().sorted(Comparator.comparing(Abc::isClickable).collect(Collectors.toList());

output: false,false,true,true,true

回答4:

I want the items with true value to appear first. My solution would be:

Collections.sort(m_mall, new Comparator<Mall>(){

        @Override
        public int compare(Mall mall1, Mall mall2){

            boolean b1 = mall1.isClickable;
            boolean b2 = mall2.isClickable;

            return (b1 != b2) ? (b1) ? -1 : 1 : 0;
        }
    });

回答5:

A simple suggestion would be to use the object Boolean instead of boolean and use Collections.sort.

However, you must know that the false will be before the true because true are represented as 1 and false as 0. But then, you could just change your algorithm and access in reverse order.

Edit : As soulscheck stated, you could use Collections.reverseOrder to revert the ordering imposed by the Comparator.

回答6:

Java 8:

 Collections.sort(abc, (abc1, abc2) ->
                  Boolean.compare(abc2.isClickable(), abc1.isClickable()));

回答7:

It is also possible that way.

myList.sort((a, b) -> Boolean.compare(a.isSn_Principal(), b.isSn_Principal()));

回答8:

Using Kotlin you can do smth like this:

listOfABCElements.sortBy { it.isClickable }

output: true,true,true,false,false

in reverse order:

listOfABCElements.sortByDescending { it.isClickable }

output: false,false,true,true,true

来源：https://stackoverflow.com/questions/28002342/sort-an-arraylist-by-primitive-boolean-type

标签

java

sorting

arraylist

java-collections-api