Differences

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--- swdev:java:lang:arraylist [2017/10/24 08:37]
smayr created
+++ 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>
-public ArrayList<Object> asArray()
+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;
+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(id);
+    arr.add(this.id);
-    arr.add(name);
+    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);
+  }
+}
+</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>