com.wantedtech.common.xpresso.helpers

Class Assert

java.lang.Object

com.wantedtech.common.xpresso.helpers.Assert

public final class Assert
extends java.lang.Object

Simple methods to be called at the start of your own methods to verify correct arguments and state. This allows constructs such as

 
     if (count <= 0) {
       throw new IllegalArgumentException("must be positive: " + count);
     }
 
 

to be replaced with the more compact

 
     isTrue(count > 0, "must be positive: %s", count);
 
 

Note that the sense of the expression is inverted; with Assert you declare what you expect to be true, just as you do with an assert or a JUnit assertTrue call.

Warning: only the "%s" specifier is recognized as a placeholder in these messages, not the full range of String.format(String, Object[]) specifiers. Take care not to confuse precondition checking with other similar types of checks! Precondition exceptions -- including those provided here, but also IndexOutOfBoundsException, NoSuchElementException, UnsupportedOperationException and others -- are used to signal that the calling method has made an error. This tells the caller that it should not have invoked the method when it did, with the arguments it did, or perhaps ever. Postcondition or other invariant failures should not throw these types of exceptions.

Constructor Summary

Constructors

Constructor and Description
Assert()

Method Summary

Modifier and Type	Method and Description
<K,V> void	notEmpty(java.util.Map<K,V> map) Assert that the specified argument map is neither null nor a size of zero (no elements); otherwise throwing an exception.
<K,V> void	notEmpty(java.util.Map<K,V> map, java.lang.String message) Assert that the specified argument map is neither null nor a size of zero (no elements); otherwise throwing an exception with the specified message.
<T> void	notEmpty(T iterable) Assert that the specified argument iterable is neither null nor a size of zero (no elements); otherwise throwing an exception.
<T> T[]	notEmpty(T[] array) Assert that the specified argument array is neither null nor a length of zero (no elements); otherwise throwing an exception.
<T> T[]	notEmpty(T[] array, java.lang.String message, java.lang.Object... values) Assert that the specified argument array is neither null nor a length of zero (no elements); otherwise throwing an exception with the specified message.
<T extends java.lang.CharSequence> void	notEmpty(T chars, java.lang.String message) Assert that the specified argument character sequence is neither null nor a length of zero (no characters); otherwise throwing an exception with the specified message.
<T> void	notEmpty(T iterable, java.lang.String message, java.lang.Object... values) Assert that the specified argument iterable is neither null nor a size of zero (no elements); otherwise throwing an exception with the specified message.
<T> T	notNull(T reference) Ensures that an object reference passed as a parameter to the calling method is not null.
<T> T	notNull(T reference, java.lang.Object errorMessage) Ensures that an object reference passed as a parameter to the calling method is not null.
<T> T	notNull(T reference, java.lang.String errorMessageTemplate, java.lang.Object... errorMessageArgs) Ensures that an object reference passed as a parameter to the calling method is not null.
void	True(boolean expression) Ensures the truth of an expression involving one or more parameters to the calling method.
void	True(boolean expression, java.lang.Object errorMessage) Ensures the truth of an expression involving one or more parameters to the calling method.
void	True(boolean expression, java.lang.String errorMessageTemplate, java.lang.Object... errorMessageArgs) Ensures the truth of an expression involving one or more parameters to the calling method.

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

Assert

public Assert()

Method Detail

True

public void True(boolean expression)

Ensures the truth of an expression involving one or more parameters to the calling method.

Parameters:

expression - a boolean expression

Throws:

java.lang.IllegalArgumentException - if expression is false

True

public void True(boolean expression,
                 java.lang.Object errorMessage)

Ensures the truth of an expression involving one or more parameters to the calling method.

Parameters:

expression - a boolean expression

errorMessage - the exception message to use if the check fails; will be converted to a string using String.valueOf(Object)

Throws:

java.lang.IllegalArgumentException - if expression is false

True

public void True(boolean expression,
                 java.lang.String errorMessageTemplate,
                 java.lang.Object... errorMessageArgs)

Ensures the truth of an expression involving one or more parameters to the calling method.

Parameters:

expression - a boolean expression

errorMessageTemplate - a template for the exception message should the check fail. The message is formed by replacing each %s placeholder in the template with an argument. These are matched by position - the first %s gets errorMessageArgs[0], etc. Unmatched arguments will be appended to the formatted message in square braces. Unmatched placeholders will be left as-is.

errorMessageArgs - the arguments to be substituted into the message template. Arguments are converted to strings using String.valueOf(Object).

Throws:

java.lang.IllegalArgumentException - if expression is false

java.lang.NullPointerException - if the check fails and either errorMessageTemplate or errorMessageArgs is null (don't let this happen)

notNull

public <T> T notNull(T reference)

Ensures that an object reference passed as a parameter to the calling method is not null.

Type Parameters:

T - any type

Parameters:

reference - an object reference

Returns:

the non-null reference that was validated

Throws:

java.lang.NullPointerException - if reference is null

notNull

public <T> T notNull(T reference,
                     java.lang.Object errorMessage)

Ensures that an object reference passed as a parameter to the calling method is not null.

Type Parameters:

T - any type

Parameters:

reference - an object reference

errorMessage - the exception message to use if the check fails; will be converted to a string using String.valueOf(Object)

Returns:

the non-null reference that was validated

Throws:

java.lang.NullPointerException - if reference is null

notNull

public <T> T notNull(T reference,
                     java.lang.String errorMessageTemplate,
                     java.lang.Object... errorMessageArgs)

Ensures that an object reference passed as a parameter to the calling method is not null.

Type Parameters:

T - any type

Parameters:

reference - an object reference

errorMessageTemplate - Template a template for the exception message should the check fail. The message is formed by replacing each %s placeholder in the template with an argument. These are matched by position - the first %s gets errorMessageArgs[0], etc. Unmatched arguments will be appended to the formatted message in square braces. Unmatched placeholders will be left as-is.

errorMessageArgs - the arguments to be substituted into the message template. Arguments are converted to strings using String.valueOf(Object).

Returns:

the non-null reference that was validated

Throws:

java.lang.NullPointerException - if reference is null

notEmpty

public <T> T[] notEmpty(T[] array,
                        java.lang.String message,
                        java.lang.Object... values)

Assert that the specified argument array is neither null nor a length of zero (no elements); otherwise throwing an exception with the specified message.

x.Assert.notEmpty(myArray, "The array must not be empty");

Type Parameters:

T - the array type

Parameters:

array - the array to check, validated not null by this method

message - the String.format(String, Object...) exception message if invalid, not null

values - the optional values for the formatted exception message, null array not recommended

Returns:

the validated array (never null method for chaining)

Throws:

java.lang.NullPointerException - if the array is null

java.lang.IllegalArgumentException - if the array is empty

See Also:

notEmpty(Object[])

notEmpty

public <T> T[] notEmpty(T[] array)

Assert that the specified argument array is neither null nor a length of zero (no elements); otherwise throwing an exception.

x.Assert.notEmpty(myArray);

The message in the exception is "The validated array is empty".

Type Parameters:

T - the array type

Parameters:

array - the array to check, validated not null by this method

Returns:

the validated array (never null method for chaining)

Throws:

java.lang.NullPointerException - if the array is null

java.lang.IllegalArgumentException - if the array is empty

See Also:

notEmpty(Object[], String, Object...)

notEmpty

public <T> void notEmpty(T iterable,
                         java.lang.String message,
                         java.lang.Object... values)

Assert that the specified argument iterable is neither null nor a size of zero (no elements); otherwise throwing an exception with the specified message.

x.Assert.notEmpty(myIterable, "The iterable must not be empty");

Type Parameters:

T - the iterable type

Parameters:

iterable - the iterable to check, validated not null by this method

message - the String.format(String, Object...) exception message if invalid, not null

values - the optional values for the formatted exception message, null array not recommended

Throws:

java.lang.NullPointerException - if the iterable is null

java.lang.IllegalArgumentException - if the iterable is empty

See Also:

notEmpty(Object[])

notEmpty

public <T> void notEmpty(T iterable)

Assert that the specified argument iterable is neither null nor a size of zero (no elements); otherwise throwing an exception.

x.Assert.notEmpty(myIterable);

The message in the exception is "The validated iterable is empty".

Type Parameters:

T - the iterable type

Parameters:

iterable - the iterable to check, validated not null by this method

Throws:

java.lang.NullPointerException - if the iterable is null

java.lang.IllegalArgumentException - if the iterable is empty

notEmpty

public <K,V> void notEmpty(java.util.Map<K,V> map,
                           java.lang.String message)

Assert that the specified argument map is neither null nor a size of zero (no elements); otherwise throwing an exception with the specified message.

x.Assert.notEmpty(myMap, "The map must not be empty");

Type Parameters:

K - the type of key

V - the type of value

Parameters:

map - the map to check, validated not null by this method

message - the String.format(String, Object...) exception message if invalid, not null

Throws:

java.lang.NullPointerException - if the map is null

java.lang.IllegalArgumentException - if the map is empty

See Also:

notEmpty(Object[])

notEmpty

public <K,V> void notEmpty(java.util.Map<K,V> map)

Assert that the specified argument map is neither null nor a size of zero (no elements); otherwise throwing an exception.

x.Assert.notEmpty(myMap);

The message in the exception is "The validated map is empty".

Type Parameters:

K - the type of key

V - the type of value

Parameters:

map - the map to check, validated not null by this method

Throws:

java.lang.NullPointerException - if the map is null

java.lang.IllegalArgumentException - if the map is empty

See Also:

notEmpty(Map, String)

notEmpty

public <T extends java.lang.CharSequence> void notEmpty(T chars,
                                                        java.lang.String message)

Assert that the specified argument character sequence is neither null nor a length of zero (no characters); otherwise throwing an exception with the specified message.

x.Assert.notEmpty(myString, "The string must not be empty");

Type Parameters:

T - the character sequence type

Parameters:

chars - the character sequence to check, validated not null by this method

message - the String.format(String, Object...) exception message if invalid, not null

Throws:

java.lang.NullPointerException - if the character sequence is null

java.lang.IllegalArgumentException - if the character sequence is empty