<p>For example:</p>

<pre><code>javac Foo.java
Note: Foo.java uses unchecked or unsafe operations.
Note: Recompile with -Xlint:unchecked for details.
</code></pre>

This comes up in Java 5 and later if you're using collections without type specifiers (e.g.,
```
Arraylist()
```
instead of
```
ArrayList<String>()
```
).  It means that the compiler can't check that you're using the collection in a type-safe way, using
generics
.
To get rid of the warning, you need to be specific about what type of objects you're storing in the collection.  So, instead of
```
```
List myList = new ArrayList();
```
```
use
```
```
List<String> myList = new ArrayList<String>();
```
```
In Java 7 you can shorten generic instantiation by using
Type Inference
.
```
```
List<String> myList = new ArrayList<>();
```
```