List
List is a generic class that can handle most data.
Initializing a List
:
import java.util.ArrayList; import java.util.List; // Method 1 List<Object> arr = Arrays.asList( 1, "10001", "Acme Inc.", 1, null ); // Method 2 List<Object> arr = new ArrayList<Object>(); arr.add(1); arr.add("10001"); arr.add("Acme Inc."); arr.add(1); arr.add(null);
ArrayList
ArrayList
is derived from List
. It can handle mixed primitives (as Object
).
import java.time.LocalDateTime; import java.util.ArrayList; import java.util.List; public class MyRecord { private Integer id; private String name; public ArrayList<Object> asArray() { ArrayList<Object> arr = new ArrayList<Object>(); arr.add(this.id); arr.add(this.name); return arr; } public void fromArray(ArrayList<Object> arr) { this.id = (Integer)arr.get(0); this.name = (String)arr.get(1); this.created_at = (LocalDateTime)arr.get(2); this.status = (Boolean)arr.get(3); } }
To process each object with the correct type:
ArrayList<Object> listOfObjects = new ArrayList<Object>(); for(Object obj: listOfObjects) { if (obj instanceof String) { // handle String } else if (obj instanceof Integer) { // handle Integer } else { // handle others } }