Differences

This shows you the differences between two versions of the page.

--- swdev:java:lang:arraylist [2017/10/25 08:32]
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 31: / Line 53: @@
 </code>
-= List =
+To process each object with the correct type:
-List is a generic class that can handle most data.
-Initializing a ''List'':
 <code java>
-import java.util.ArrayList;
+ArrayList<Object> listOfObjects = new ArrayList<Object>();
-import java.util.List;
+for(Object obj: listOfObjects) {
+   if (obj instanceof String) {
-// Method 1
+       // handle String
-List<Object> arr = Arrays.asList(
+   } else if (obj instanceof Integer) {
-, "10001", "Acme Inc.", 1, null
+       // handle Integer
-);
+   } else {
+       // handle others
-// 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>