Assumption (GraalVM Truffle Java API Reference)

```
public interface Assumption
```
An assumption is a global boolean flag that starts with the value true (i.e., the assumption is valid) and can subsequently be invalidated (using Assumption.invalidate()). Once invalidated, an assumption can never get valid again. Assumptions can be created using the TruffleRuntime.createAssumption() or the TruffleRuntime.createAssumption(String) method. The Truffle compiler has special knowledge of this class in order to produce efficient machine code for checking an assumption in case the assumption object is a compile time constant. Therefore, assumptions should be stored in final fields in Truffle nodes. All instances of classes implementing Assumption must be held in final fields for compiler optimizations to take effect.
Do not manually subclass the Assumption interface. This class is only intended to be subclassed by Truffle runtime implementations to avoid polymorphism in performance sensitive methods.

Since:

0.8 or earlier

Field Summary

Fields
Modifier and Type	Field and Description
`static Assumption`	`ALWAYS_VALID` An assumption that is always valid and fails with an `UnsupportedOperationException` if invalidated.
`static Assumption`	`NEVER_VALID` An assumption that is never valid.

Method Summary

All Methods Static Methods Instance Methods Abstract Methods Default Methods
Modifier and Type	Method and Description
`void`	`check()` Checks that this assumption is still valid.
`static Assumption`	`create()` Creates a new assumption with a name.
`static Assumption`	`create(String name)` Creates a new assumption with a name.
`String`	`getName()` A name for the assumption that is used for debug output.
`void`	`invalidate()` Invalidates this assumption.
`default void`	`invalidate(String message)` Invalidates this assumption.
`boolean`	`isValid()` Checks whether the assumption is still valid.
`static boolean`	`isValidAssumption(Assumption assumption)` Checks whether an assumption is not `null` and valid.
`static boolean`	`isValidAssumption(Assumption[] assumptions)` Checks whether all assumptions in an array are not `null` and valid.

- Field Detail
  - ALWAYS_VALID
```
static final Assumption ALWAYS_VALID
```
    An assumption that is always valid and fails with an UnsupportedOperationException if invalidated.
    
    Since:
    
    22.1
  - NEVER_VALID
```
static final Assumption NEVER_VALID
```
    An assumption that is never valid.
    
    Since:
    
    22.1
- Method Detail
  - check
```
void check()
    throws InvalidAssumptionException
```
    Checks that this assumption is still valid. The method throws an exception, if this is no longer the case. This method is preferred over the Assumption.isValid() method when writing guest language interpreter code. The catch block should perform a node rewrite (see Node.replace(Node)) with a node that no longer relies on the assumption.
    
    Throws:
    
    InvalidAssumptionException - If the assumption is no longer valid.
    
    Since:
    
    0.8 or earlier
  - isValid
```
boolean isValid()
```
    Checks whether the assumption is still valid.
    
    Returns:
    
    a boolean value indicating the validity of the assumption
    
    Since:
    
    0.8 or earlier
  - invalidate
```
void invalidate()
```
    Invalidates this assumption. Performs no operation, if the assumption is already invalid.
    
    Since:
    
    0.8 or earlier
  - invalidate
```
default void invalidate(String message)
```
    Invalidates this assumption. Performs no operation, if the assumption is already invalid.
    
    Parameters:
    
    message - a message stating the reason of the invalidation
    
    Since:
    
    0.33
  - getName
```
String getName()
```
    A name for the assumption that is used for debug output.
    
    Returns:
    
    the name of the assumption
    
    Since:
    
    0.8 or earlier
  - isValidAssumption
```
static boolean isValidAssumption(Assumption assumption)
```
    Checks whether an assumption is not null and valid.
    
    Since:
    
    19.0
  - isValidAssumption
```
static boolean isValidAssumption(Assumption[] assumptions)
```
    Checks whether all assumptions in an array are not null and valid. Returns false if the assumptions array itself is null. This method is designed for compilation. Note that the provided assumptions array must be a compilation final array with dimensions set to one.
    
    Since:
    
    19.0
  - create
```
static Assumption create()
```
    Creates a new assumption with a name. Shortcut for TruffleRuntime.createAssumption().
    
    Since:
    
    22.1
  - create
```
static Assumption create(String name)
```
    Creates a new assumption with a name. Shortcut for TruffleRuntime.createAssumption(String).
    
    Since:
    
    22.1

Interface Assumption

Field Summary

Method Summary

Field Detail

ALWAYS_VALID

NEVER_VALID

Method Detail

check

isValid

invalidate

invalidate

getName

isValidAssumption

isValidAssumption

create

create