You can use the `filter`

operator to filter out items from the values stream based on a result of a predicate method.

In other words, the items passing from the Observer to the Subscriber will be discarded based on the Function you pass `filter`

, if the function returns `false`

for a certain value, that value will be filtered out.

**Example:**

```
List<Integer> integers = Arrays.asList(0, 1, 2, 3, 4, 5, 6, 7, 8, 9);
Observable.from(integers)
.filter(number -> {
return (number % 2 == 0);
// odd numbers will return false, that will cause them to be filtered
})
.map(i -> {
return Math.pow(i, 2); // take each number and multiply by power of 2
})
.subscribe(onNext -> {
System.out.println(onNext); // print out the remaining numbers
});
```

This code will print out

```
0.0
4.0
16.0
36.0
64.0
```