com.github.valid8j.classic

Enum Assertions

java.lang.Object

java.lang.Enum<Assertions>

com.github.valid8j.classic.Assertions

All Implemented Interfaces:

Serializable, Comparable<Assertions>

public enum Assertions
extends Enum<Assertions>

Use methods in this class with the assert statement.

import static com.github.valid8j.pcond.core.functions.Predicates.isNotNull;
import static com.github.valid8j.pcond.classic.Assertions.*

public class TestClass {
  public static void aMethod(Object value) {
    assert that(value, isNotNull());
  }
}

This prints a much more readable error message than one you see for a usual assertion failure.

Exception in thread "main" java.lang.AssertionError: Value:null violated: isNotNull
null -> isNotNull -> false
        at com.github.valid8j.pcond.provider.impls.DefaultAssertionProvider.checkValue(DefaultAssertionProvider.java:70)
        at com.github.valid8j.pcond.provider.AssertionProviderBase.checkInvariant(AssertionProviderBase.java:78)
        at com.github.valid8j.pcond.classic.Assertions.that(Assertions.java:51)
        ...

To enable this feature, do not forget giving -ea VM option to enable assertions. Otherwise, the evaluation doesn’t happen completely and even printable predicates constructed the right side of the assert statement. This means you can enable the feature during the development and disable it in the production so that you will not see no performance impact.

Method Summary

Modifier and Type	Method and Description
static <T> boolean	postcondition(T value, Predicate<? super T> predicate) A method to be used for checking a value satisfies a given post-condition.
static <T> boolean	precondition(T value, Predicate<? super T> predicate) A method to be used for checking a value satisfies a given pre-condition.
static <T> boolean	that(T value, Predicate<? super T> predicate) A method to be used for checking a value satisfies a given invariant condition.
static Assertions	valueOf(String name) Returns the enum constant of this type with the specified name.
static Assertions[]	values() Returns an array containing the constants of this enum type, in the order they are declared.

Methods inherited from class java.lang.Enum

clone, compareTo, equals, finalize, getDeclaringClass, hashCode, name, ordinal, toString, valueOf

Methods inherited from class java.lang.Object

getClass, notify, notifyAll, wait, wait, wait

Method Detail

values

public static Assertions[] values()

Returns an array containing the constants of this enum type, in the order they are declared. This method may be used to iterate over the constants as follows:

for (Assertions c : Assertions.values())
    System.out.println(c);

Returns:

an array containing the constants of this enum type, in the order they are declared

valueOf

public static Assertions valueOf(String name)

Returns the enum constant of this type with the specified name. The string must match exactly an identifier used to declare an enum constant in this type. (Extraneous whitespace characters are not permitted.)

Parameters:

name - the name of the enum constant to be returned.

Returns:

the enum constant with the specified name

Throws:

IllegalArgumentException - if this enum type has no constant with the specified name

NullPointerException - if the argument is null

that

public static <T> boolean that(T value,
                               Predicate<? super T> predicate)

A method to be used for checking a value satisfies a given invariant condition. This method is intended to be used in assert statements.

Example

public void aMethod(String var) {
assert that(var, isNotNull());
}

Type Parameters:

T - The type of value.

Parameters:

value - A value to be checked.

predicate - An invariant condition to check the value.

Returns:

true, if the condition given as predicate is satisfied.

precondition

public static <T> boolean precondition(T value,
                                       Predicate<? super T> predicate)

A method to be used for checking a value satisfies a given pre-condition. This method is intended to be used in assert statements.

Example

public void aMethod(String var) {
assert precondition(var, isNotNull());
}

Type Parameters:

T - The type of value.

Parameters:

value - A value to be checked.

predicate - A pre-condition to check the value.

Returns:

true, if the condition given as predicate is satisfied.

postcondition

public static <T> boolean postcondition(T value,
                                        Predicate<? super T> predicate)

A method to be used for checking a value satisfies a given post-condition. This method is intended to be used in assert statements.

Example

public void aMethod(String var) {
assert postcondition(var, isNotNull());
}

Type Parameters:

T - The type of value.

Parameters:

value - A value to be checked.

predicate - A post-condition to check the value.

Returns:

true, if the condition given as predicate is satisfied.