Java Module jdk.dynalink Package jdk.dynalink.linker.support Class Guards（JDK11）

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java.lang.Object
- jdk.dynalink.linker.support.Guards

```
public final class Guards
extends Object
```
Utility methods for creating typical guards for MethodHandles.guardWithTest(MethodHandle, MethodHandle, MethodHandle) and for adjusting their method types.

Method Summary

All Methods Static Methods Concrete Methods
Modifier and Type	Method	Description
`static MethodHandle`	`asType(MethodHandle test, MethodType type)`	Takes a method handle intended to be used as a guard, and adapts it to the requested type, but returning a boolean.
`static MethodHandle`	`asType(LinkerServices linkerServices, MethodHandle test, MethodType type)`	Takes a method handle intended to be used as a guard, and adapts it to the requested type, but returning a boolean.
`static MethodHandle`	`getClassGuard(Class<?> clazz)`	Creates a guard method that tests its only argument for being of an exact particular class.
`static MethodHandle`	`getIdentityGuard(Object obj)`	Creates a guard method that tests its only argument for being referentially identical to another object
`static MethodHandle`	`getInstanceOfGuard(Class<?> clazz)`	Creates a guard method that tests its only argument for being an instance of a particular class.
`static MethodHandle`	`isArray(int pos, MethodType type)`	Creates a method handle that returns true if the argument in the specified position is a Java array.
`static MethodHandle`	`isInstance(Class<?> clazz, int pos, MethodType type)`	Creates a method handle with arguments of a specified type, but with boolean return value.
`static MethodHandle`	`isInstance(Class<?> clazz, MethodType type)`	Creates a method handle with arguments of a specified type, but with boolean return value.
`static MethodHandle`	`isNotNull()`	Returns a guard that tests whether the first argument is not null.
`static MethodHandle`	`isNull()`	Returns a guard that tests whether the first argument is null.
`static MethodHandle`	`isOfClass(Class<?> clazz, MethodType type)`	Creates a guard method handle with arguments of a specified type, but with boolean return value.

Methods declared in class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Method Detail
  - isOfClass
```
public static MethodHandle isOfClass(Class<?> clazz,
                                     MethodType type)
```
    Creates a guard method handle with arguments of a specified type, but with boolean return value. When invoked, it returns true if the first argument is of the specified class (exactly of it, not a subclass). The rest of the arguments will be ignored.
    
    Parameters:
    
    clazz - the class of the first argument to test for
    
    type - the method type
    
    Returns:
    
    a method handle testing whether its first argument is of the specified class.
  - isInstance
```
public static MethodHandle isInstance(Class<?> clazz,
                                      MethodType type)
```
    Creates a method handle with arguments of a specified type, but with boolean return value. When invoked, it returns true if the first argument is instance of the specified class or its subclass). The rest of the arguments will be ignored.
    
    Parameters:
    
    clazz - the class of the first argument to test for
    
    type - the method type
    
    Returns:
    
    a method handle testing whether its first argument is of the specified class or subclass.
  - isInstance
```
public static MethodHandle isInstance(Class<?> clazz,
                                      int pos,
                                      MethodType type)
```
    Creates a method handle with arguments of a specified type, but with boolean return value. When invoked, it returns true if the n'th argument is instance of the specified class or its subclass). The rest of the arguments will be ignored.
    
    Parameters:
    
    clazz - the class of the first argument to test for
    
    pos - the position on the argument list to test
    
    type - the method type
    
    Returns:
    
    a method handle testing whether its first argument is of the specified class or subclass.
  - isArray
```
public static MethodHandle isArray(int pos,
                                   MethodType type)
```
    Creates a method handle that returns true if the argument in the specified position is a Java array.
    
    Parameters:
    
    pos - the position in the argument lit
    
    type - the method type of the handle
    
    Returns:
    
    a method handle that returns true if the argument in the specified position is a Java array; the rest of the arguments are ignored.
  - asType
```
public static MethodHandle asType(MethodHandle test,
                                  MethodType type)
```
    Takes a method handle intended to be used as a guard, and adapts it to the requested type, but returning a boolean. Applies MethodHandle.asType(MethodType) to convert types and uses MethodHandles.dropArguments(MethodHandle, int, Class...) to match the requested type arity.
    
    Parameters:
    
    test - the test method handle
    
    type - the type to adapt the method handle to
    
    Returns:
    
    the adapted method handle
  - asType
```
public static MethodHandle asType(LinkerServices linkerServices,
                                  MethodHandle test,
                                  MethodType type)
```
    Takes a method handle intended to be used as a guard, and adapts it to the requested type, but returning a boolean. Applies LinkerServices.asType(MethodHandle, MethodType) to convert types and uses MethodHandles.dropArguments(MethodHandle, int, Class...) to match the requested type arity.
    
    Parameters:
    
    linkerServices - the linker services to use for type conversions
    
    test - the test method handle
    
    type - the type to adapt the method handle to
    
    Returns:
    
    the adapted method handle
  - getClassGuard
```
public static MethodHandle getClassGuard(Class<?> clazz)
```
    Creates a guard method that tests its only argument for being of an exact particular class.
    
    Parameters:
    
    clazz - the class to test for.
    
    Returns:
    
    the desired guard method.
  - getInstanceOfGuard
```
public static MethodHandle getInstanceOfGuard(Class<?> clazz)
```
    Creates a guard method that tests its only argument for being an instance of a particular class.
    
    Parameters:
    
    clazz - the class to test for.
    
    Returns:
    
    the desired guard method.
  - getIdentityGuard
```
public static MethodHandle getIdentityGuard(Object obj)
```
    Creates a guard method that tests its only argument for being referentially identical to another object
    
    Parameters:
    
    obj - the object used as referential identity test
    
    Returns:
    
    the desired guard method.
  - isNull
```
public static MethodHandle isNull()
```
    Returns a guard that tests whether the first argument is null.
    
    Returns:
    
    a guard that tests whether the first argument is null.
  - isNotNull
```
public static MethodHandle isNotNull()
```
    Returns a guard that tests whether the first argument is not null.
    
    Returns:
    
    a guard that tests whether the first argument is not null.

Java Module jdk.dynalink Package jdk.dynalink.linker.support Class Guards（JDK11）

Class Guards

Method Summary

Methods declared in class java.lang.Object

Method Detail

isOfClass

isInstance

isInstance

isArray

asType

asType

getClassGuard

getInstanceOfGuard

getIdentityGuard

isNull

isNotNull