docs/javadoc/reference/com/facebook/common/internal/Preconditions.html
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ImmutableMap<K, V>
ImmutableSet<E>
Summary: Methods | Inherited Methods | [Expand All]
public final class
extends Object
| java.lang.Object | | ↳ | com.facebook.common.internal.Preconditions |
Static convenience methods that help a method or constructor check whether it was invoked correctly (whether its preconditions have been met). These methods generally accept a boolean expression which is expected to be true (or in the case of checkNotNull, an object reference which is expected to be non-null). When false (or null) is passed instead, the Preconditions method throws an unchecked exception, which helps the calling method communicate to its caller that that caller has made a mistake. Example:
/**
* Returns the positive square root of the given value.
*
* @throws IllegalArgumentException if the value is negative
*/
public static double sqrt(double value) {
Preconditions.checkArgument(value >= 0.0, "negative value: %s", value);
// calculate the square rootvoid exampleBadCaller() {
double d = sqrt(-1.0);
}
}
In this example, checkArgument throws an IllegalArgumentException to indicate that exampleBadCaller made an error in its call to sqrt.
The goal of this class is to improve readability of code, but in some circumstances this may come at a significant performance cost. Remember that parameter values for message construction must all be computed eagerly, and autoboxing and varargs array creation may happen as well, even when the precondition check then succeeds (as it should almost always do in production). In some circumstances these wasted CPU cycles and allocations can add up to a real problem. Performance-sensitive precondition checks can always be converted to the customary form:
if (value < 0.0) {
throw new IllegalArgumentException("negative value: " + value);}
Not every type of precondition failure is supported by these methods. Continue to throw standard JDK exceptions such as java.util.NoSuchElementException or UnsupportedOperationException in the situations they are intended for.
It is of course possible to use the methods of this class to check for invalid conditions which are not the caller's fault. Doing so is not recommended because it is misleading to future readers of the code and of stack traces. See Conditional failures explained in the Guava User Guide for more advice.
java.util.Objects.requireNonNull()Projects which use com.google.common should generally avoid the use of requireNonNull(Object). Instead, use whichever of checkNotNull(Object) or Verify#verifyNotNull(Object) is appropriate to the situation. (The same goes for the message-accepting overloads.)
%s is supportedIn Preconditions error message template strings, only the "%s" specifier is supported, not the full range of java.util.Formatter specifiers. However, note that if the number of arguments does not match the number of occurrences of "%s" in the format string, Preconditions will still behave as expected, and will still include all argument values in the error message; the message will simply not be formatted exactly as intended.
See the Guava User Guide on using Preconditions.
| Public Methods |
|---|
| static void |
| Ensures the truth of an expression involving one or more parameters to the calling method. |
| static void |
| Ensures the truth of an expression involving one or more parameters to the calling method. |
| static void |
| Ensures the truth of an expression involving one or more parameters to the calling method. |
| static int |
Ensures that index specifies a valid element in an array, list or string of size size. |
| static int |
Ensures that index specifies a valid element in an array, list or string of size size. |
| static <T> T |
| Ensures that an object reference passed as a parameter to the calling method is not null. |
| static <T> T |
| Ensures that an object reference passed as a parameter to the calling method is not null. |
| static <T> T |
| Ensures that an object reference passed as a parameter to the calling method is not null. |
| static int |
Ensures that index specifies a valid position in an array, list or string of size size. |
| static int |
Ensures that index specifies a valid position in an array, list or string of size size. |
| static void |
Ensures that start and end specify a valid positions in an array, list or string of size size, and are in order. |
| static void |
| Ensures the truth of an expression involving the state of the calling instance, but not involving any parameters to the calling method. |
| static void |
| Ensures the truth of an expression involving the state of the calling instance, but not involving any parameters to the calling method. |
| static void |
| Ensures the truth of an expression involving the state of the calling instance, but not involving any parameters to the calling method. |
| [Expand] Inherited Methods | | --- | | From class java.lang.Object
| Object | clone() | | boolean | equals(Object arg0) | | void | finalize() | | final Class<?> | getClass() | | int | hashCode() | | final void | notify() | | final void | notifyAll() | | String | toString() | | final void | wait(long arg0, int arg1) | | final void | wait(long arg0) | | final void | wait() |
|
Ensures the truth of an expression involving one or more parameters to the calling method.
| 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 valueOf(Object). |
| IllegalArgumentException | if expression is false |
| NullPointerException | if the check fails and either errorMessageTemplate or errorMessageArgs is null (don't let this happen) |
Ensures the truth of an expression involving one or more parameters to the calling method.
| expression | a boolean expression |
| IllegalArgumentException | if expression is false |
Ensures the truth of an expression involving one or more parameters to the calling method.
| expression | a boolean expression |
| errorMessage | the exception message to use if the check fails; will be converted to a string using valueOf(Object) |
| IllegalArgumentException | if expression is false |
Ensures that index specifies a valid element in an array, list or string of size size. An element index may range from zero, inclusive, to size, exclusive.
| index | a user-supplied index identifying an element of an array, list or string | | size | the size of that array, list or string | | desc | the text to use to describe this index in an error message |
index| IndexOutOfBoundsException | if index is negative or is not less than size |
| IllegalArgumentException | if size is negative |
Ensures that index specifies a valid element in an array, list or string of size size. An element index may range from zero, inclusive, to size, exclusive.
| index | a user-supplied index identifying an element of an array, list or string | | size | the size of that array, list or string |
index| IndexOutOfBoundsException | if index is negative or is not less than size |
| IllegalArgumentException | if size is negative |
Ensures that an object reference passed as a parameter to the calling method is not null.
| reference | an object reference |
| errorMessage | the exception message to use if the check fails; will be converted to a string using valueOf(Object) |
| NullPointerException | if reference is null |
Ensures that an object reference passed as a parameter to the calling method is not null.
| reference | an object reference |
| 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 valueOf(Object). |
| NullPointerException | if reference is null |
Ensures that an object reference passed as a parameter to the calling method is not null.
| reference | an object reference |
| NullPointerException | if reference is null |
Ensures that index specifies a valid position in an array, list or string of size size. A position index may range from zero to size, inclusive.
| index | a user-supplied index identifying a position in an array, list or string | | size | the size of that array, list or string | | desc | the text to use to describe this index in an error message |
index| IndexOutOfBoundsException | if index is negative or is greater than size |
| IllegalArgumentException | if size is negative |
Ensures that index specifies a valid position in an array, list or string of size size. A position index may range from zero to size, inclusive.
| index | a user-supplied index identifying a position in an array, list or string | | size | the size of that array, list or string |
index| IndexOutOfBoundsException | if index is negative or is greater than size |
| IllegalArgumentException | if size is negative |
Ensures that start and end specify a valid positions in an array, list or string of size size, and are in order. A position index may range from zero to size, inclusive.
| start | a user-supplied index identifying a starting position in an array, list or string | | end | a user-supplied index identifying a ending position in an array, list or string | | size | the size of that array, list or string |
| IndexOutOfBoundsException | if either index is negative or is greater than size, or if end is less than start |
| IllegalArgumentException | if size is negative |
Ensures the truth of an expression involving the state of the calling instance, but not involving any parameters to the calling method.
| expression | a boolean expression |
| errorMessage | the exception message to use if the check fails; will be converted to a string using valueOf(Object) |
| IllegalStateException | if expression is false |
Ensures the truth of an expression involving the state of the calling instance, but not involving any parameters to the calling method.
| 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 valueOf(Object). |
| IllegalStateException | if expression is false |
| NullPointerException | if the check fails and either errorMessageTemplate or errorMessageArgs is null (don't let this happen) |
Ensures the truth of an expression involving the state of the calling instance, but not involving any parameters to the calling method.
| expression | a boolean expression |
| IllegalStateException | if expression is false |
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