java - Sort List of Objects by values from array; -

i have list<brand> categories; 1000+ items.

for each item list have id, use categories.getid();

and have array int[] sortedidarr = {4,53,102,403,110,5,6,8,12};

i sort categories list , make order id how in sortedidarr. how can implement ?

private void sortbrandsbyid(list<brand> categories) {     collections.sort(categories, new comparator<brand>() {         public int compare(brand o1, brand o2) {          }     });     } 

can use collections.sort ?

typically use collections.sort, or equivalent idioms in java 8 if applicable, or sorted collection such treeset.

however in case want follow pre-defined order, dictated sortedidarr array.

one way achieve use linked collection (e.g. linkedhashset).

then iterate sortedidarr array, , search list<brand> object given id.

if found, add brand object given id linkedhashset, retain insertion order.

note if id not found, set not "match" array.

self-enclosed example, using java 8

package test;  import java.util.arraylist; import java.util.arrays; import java.util.linkedhashset; import java.util.list; import java.util.optional; import java.util.set;   public class main {      // simplified brand pojo     static class brand {         int id;         public brand(int id) {             this.id = id;         }         public int getid() {             return id;         }          // output clarity         @override         public string tostring() {             return string.format("brand: %d", id);         }     }      public static void main(string[] args) throws exception {          // simplified id list         int[] sortedidarr = {4,53,102};         // "randomly" ordered brand list         final list<brand> categories = new arraylist<brand>() {               {                 add(new brand(1));                 add(new brand(102));                 add(new brand(53));                 add(new brand(4));                 add(new brand(0));             }         };         // destination: linked set         set<brand> linked = new linkedhashset<brand>();         // streaming id array in order         arrays.stream(sortedidarr)             .foreach((i) -> {                 // retrieving brand same id current                 // "randomly" ordered list                 optional<brand> toadd = categories.stream()                 .filter((b) -> b.getid() == i)                 .findfirst();                 // making sure there's 1                 if (toadd.ispresent()) {                     // adding linked set                     linked.add(toadd.get());                 }             }         );         system.out.println(linked);     }  } 

output

[brand: 4, brand: 53, brand: 102] 

imperative idiom older java versions

for (int i: sortedidarr) {     (brand b: categories) {         // assuming no nulls         if (b.getid() == i) {             linked.add(b);             break;         }     } }