IndexFor (checker-framework 3.39.0-eisop1 API)

```
@Documented
@Retention(RUNTIME)
@Target({TYPE_USE,TYPE_PARAMETER})
public @interface IndexFor
```
An integer that can be used to index any of the given sequences.
For example, an expression with type @IndexFor({"a", "b"}) is non-negative and is less than both a.length and b.length. The sequences a and b might have different lengths.
The String.charAt(int) method is declared as
```
 class String {
   char charAt(@IndexFor("this") index) { ... }
 }
 
```
Writing @IndexFor("arr") is equivalent to writing @NonNegative @LTLengthOf("arr"), and that is how it is treated internally by the checker. Thus, if you write an @IndexFor("arr") annotation, you might see warnings about @NonNegative or @LTLengthOf.
See Also:

NonNegative, LTLengthOf

See the Checker Framework Manual:
Index Checker

- Required Element Summary
  
  Required Elements
  Modifier and Type Required Element Description
  
  java.lang.String[] value
  Sequences that the annotated expression is a valid index for.

- Element Detail
  - value
```
java.lang.String[] value
```
    Sequences that the annotated expression is a valid index for.