Package org.apache.hadoop.util

Class Preconditions

java.lang.Object

org.apache.hadoop.util.Preconditions

@Private
@Unstable
public final class Preconditions
extends java.lang.Object

This class replaces guava.Preconditions which provides helpers to validate the following conditions:

• An invalid null obj causes a NullPointerException.
• An invalid argument causes an IllegalArgumentException.
• An invalid state causes an IllegalStateException.
• An invalid index causes an IndexOutOfBoundsException.

Method Summary

Modifier and Type	Method	Description
static void	checkArgument(boolean expression)	Ensures the truth of an expression involving one or more parameters to the calling method.
static void	checkArgument(boolean expression, java.lang.Object errorMessage)	Ensures the truth of an expression involving one or more parameters to the calling method.
static void	checkArgument(boolean expression, java.lang.String errorMsg, java.lang.Object... errorMsgArgs)	Ensures the truth of an expression involving one or more parameters to the calling method.
static void	checkArgument(boolean expression, java.util.function.Supplier<java.lang.String> msgSupplier)	Preconditions that the expression involving one or more parameters to the calling method.
static <T> T	checkNotNull(T obj)	Preconditions that the specified argument is not null, throwing a NPE exception otherwise.
static <T> T	checkNotNull(T obj, java.lang.Object errorMessage)	Preconditions that the specified argument is not null, throwing a NPE exception otherwise.
static <T> T	checkNotNull(T obj, java.lang.String message, java.lang.Object... values)	Preconditions that the specified argument is not null, throwing a NPE exception otherwise.
static <T> T	checkNotNull(T obj, java.util.function.Supplier<java.lang.String> msgSupplier)	Preconditions that the specified argument is not null, throwing a NPE exception otherwise.
static void	checkState(boolean expression)	Ensures the truth of an expression involving the state of the calling instance without involving any parameters to the calling method.
static void	checkState(boolean expression, java.lang.Object errorMessage)	Ensures the truth of an expression involving the state of the calling instance without involving any parameters to the calling method.
static void	checkState(boolean expression, java.lang.String errorMsg, java.lang.Object... errorMsgArgs)	Ensures the truth of an expression involving the state of the calling instance without involving any parameters to the calling method.
static void	checkState(boolean expression, java.util.function.Supplier<java.lang.String> msgSupplier)	Preconditions that the expression involving one or more parameters to the calling method.

Methods inherited from class java.lang.Object

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

Method Detail

checkNotNull

public static <T> T checkNotNull(T obj)

Preconditions that the specified argument is not null, throwing a NPE exception otherwise.

The message of the exception is "The validated object is null".

Type Parameters:

T - the object type

Parameters:

obj - the object to check

Returns:

the validated object

Throws:

java.lang.NullPointerException - if the object is null

See Also:

checkNotNull(Object, Object)

checkNotNull

public static <T> T checkNotNull(T obj,
                                 java.lang.Object errorMessage)

Preconditions that the specified argument is not null, throwing a NPE exception otherwise.

The message of the exception is errorMessage.

Type Parameters:

T - the object type

Parameters:

obj - the object to check

errorMessage - the message associated with the NPE

Returns:

the validated object

Throws:

java.lang.NullPointerException - if the object is null

See Also:

checkNotNull(Object, String, Object...)

checkNotNull

public static <T> T checkNotNull(T obj,
                                 java.lang.String message,
                                 java.lang.Object... values)

Preconditions that the specified argument is not null, throwing a NPE exception otherwise.

The message of the exception is String.format(f, m).

Type Parameters:

T - the object type

Parameters:

obj - the object to check

message - the String.format(String, Object...) exception message if valid. Otherwise, the message is VALIDATE_IS_NOT_NULL_EX_MESSAGE

values - the optional values for the formatted exception message

Returns:

the validated object

Throws:

java.lang.NullPointerException - if the object is null

See Also:

checkNotNull(Object, Supplier)

checkNotNull

public static <T> T checkNotNull(T obj,
                                 java.util.function.Supplier<java.lang.String> msgSupplier)

Preconditions that the specified argument is not null, throwing a NPE exception otherwise.

The message of the exception is msgSupplier.get().

Type Parameters:

T - the object type

Parameters:

obj - the object to check

msgSupplier - the Supplier.get() set the exception message if valid. Otherwise, the message is VALIDATE_IS_NOT_NULL_EX_MESSAGE

Returns:

the validated object (never null for method chaining)

Throws:

java.lang.NullPointerException - if the object is null

checkArgument

public static void checkArgument(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

checkArgument

public static void checkArgument(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

checkArgument

public static void checkArgument(boolean expression,
                                 java.lang.String errorMsg,
                                 java.lang.Object... errorMsgArgs)

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

The message of the exception is String.format(f, m).

Parameters:

expression - a boolean expression

errorMsg - the String.format(String, Object...) exception message if valid. Otherwise, the message is CHECK_ARGUMENT_EX_MESSAGE

errorMsgArgs - the optional values for the formatted exception message.

Throws:

java.lang.IllegalArgumentException - if expression is false

checkArgument

public static void checkArgument(boolean expression,
                                 java.util.function.Supplier<java.lang.String> msgSupplier)

Preconditions that the expression involving one or more parameters to the calling method.

The message of the exception is msgSupplier.get().

Parameters:

expression - a boolean expression

msgSupplier - the Supplier.get() set the exception message if valid. Otherwise, the message is CHECK_ARGUMENT_EX_MESSAGE

Throws:

java.lang.IllegalArgumentException - if expression is false

checkState

public static void checkState(boolean expression)

Ensures the truth of an expression involving the state of the calling instance without involving any parameters to the calling method.

Parameters:

expression - a boolean expression

Throws:

java.lang.IllegalStateException - if expression is false

checkState

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

Ensures the truth of an expression involving the state of the calling instance without involving any 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.IllegalStateException - if expression is false

checkState

public static void checkState(boolean expression,
                              java.lang.String errorMsg,
                              java.lang.Object... errorMsgArgs)

Ensures the truth of an expression involving the state of the calling instance without involving any parameters to the calling method.

The message of the exception is String.format(f, m).

Parameters:

expression - a boolean expression

errorMsg - the String.format(String, Object...) exception message if valid. Otherwise, the message is CHECK_STATE_EX_MESSAGE

errorMsgArgs - the optional values for the formatted exception message.

Throws:

java.lang.IllegalStateException - if expression is false

checkState

public static void checkState(boolean expression,
                              java.util.function.Supplier<java.lang.String> msgSupplier)

Preconditions that the expression involving one or more parameters to the calling method.

The message of the exception is msgSupplier.get().

Parameters:

expression - a boolean expression

msgSupplier - the Supplier.get() set the exception message if valid. Otherwise, the message is CHECK_STATE_EX_MESSAGE

Throws:

java.lang.IllegalStateException - if expression is false