Differences

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--- swdev:java:lang:arraylist [2017/10/25 08:25]
smayr
+++ swdev:java:lang:arraylist [2017/10/25 08:49] (current)
smayr [ArrayList]
@@ Line 1: / Line 1: @@
-= ArrayList =
+= List =
+List is a generic class that can handle most data.
+Initializing a ''List'':
+<code java>
+import java.util.ArrayList;
+import java.util.List;
+// Method 1
+List<Object> arr = Arrays.asList(
+, "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);
+</code>
+= ArrayList =
+''ArrayList'' is derived from ''List''. It can handle mixed primitives (as ''Object'').
 <code java>
 import java.time.LocalDateTime;
@@ Line 21: / Line 43: @@
   }
-  public void fromArray(List<Object> 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(3);
+    this.created_at  = (LocalDateTime)arr.get(2);
-    this.status      = (Boolean)arr.get(4);
+    this.status      = (Boolean)arr.get(3);
   }
 }
 </code>
+To process each object with the correct type:
+<code java>
+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
+   }
+}
+</code>