java.lang.Object
- com.google.common.base.Preconditions

```
@GwtCompatible
public final class Preconditions
extends Object
```
Static convenience methods that help a method or constructor check whether it was invoked correctly (that is, whether its preconditions were met).
If the precondition is not met, the Preconditions method throws an unchecked exception of a specified type, which helps the method in which the exception was thrown communicate that its caller has made a mistake. This allows constructs such as
```
 public static double sqrt(double value) {
   if (value < 0) {
     throw new IllegalArgumentException("input is negative: " + value);
   }
   // calculate square root
 }
 
```
to be replaced with the more compact
```
 public static double sqrt(double value) {
   checkArgument(value >= 0, "input is negative: %s", value);
   // calculate square root
 }
 
```
so that a hypothetical bad caller of this method, such as:
```
 void exampleBadCaller() {
   double d = sqrt(-1.0);
 }
 
```
would be flagged as having called sqrt() with an illegal argument.
Performance

Avoid passing message arguments that are expensive to compute; your code will always compute them, even though they usually won't be needed. If you have such arguments, use the conventional if/throw idiom instead.
Depending on your message arguments, memory may be allocated for boxing and varargs array creation. However, the methods of this class have a large number of overloads that prevent such allocations in many common cases.
The message string is not formatted unless the exception will be thrown, so the cost of the string formatting itself should not be a concern.
As with any performance concerns, you should consider profiling your code (in a production environment if possible) before spending a lot of effort on tweaking a particular element.
Other types of preconditions

Not every type of precondition failure is supported by these methods. Continue to throw standard JDK exceptions such as NoSuchElementException or UnsupportedOperationException in the situations they are intended for.
Non-preconditions

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. Notably, Verify offers assertions similar to those in this class for non-precondition checks.
java.util.Objects.requireNonNull()

Projects which use com.google.common should generally avoid the use of Objects.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.)
Only %s is supported

Preconditions uses Strings.lenientFormat(java.lang.String, java.lang.Object...) to format error message template strings. This only supports the "%s" specifier, not the full range of 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.
More information

See the Guava User Guide on using Preconditions.
Since:

2.0

Author:

Kevin Bourrillion

Method Summary

All Methods Static Methods Concrete Methods
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, @Nullable Object errorMessage)`	Ensures the truth of an expression involving one or more parameters to the calling method.
`static void`	`checkArgument(boolean b, @Nullable String errorMessageTemplate, char p1)`	Ensures the truth of an expression involving one or more parameters to the calling method.
`static void`	`checkArgument(boolean b, @Nullable String errorMessageTemplate, char p1, char p2)`	Ensures the truth of an expression involving one or more parameters to the calling method.
`static void`	`checkArgument(boolean b, @Nullable String errorMessageTemplate, char p1, int p2)`	Ensures the truth of an expression involving one or more parameters to the calling method.
`static void`	`checkArgument(boolean b, @Nullable String errorMessageTemplate, char p1, long p2)`	Ensures the truth of an expression involving one or more parameters to the calling method.
`static void`	`checkArgument(boolean b, @Nullable String errorMessageTemplate, char p1, @Nullable Object p2)`	Ensures the truth of an expression involving one or more parameters to the calling method.
`static void`	`checkArgument(boolean b, @Nullable String errorMessageTemplate, int p1)`	Ensures the truth of an expression involving one or more parameters to the calling method.
`static void`	`checkArgument(boolean b, @Nullable String errorMessageTemplate, int p1, char p2)`	Ensures the truth of an expression involving one or more parameters to the calling method.
`static void`	`checkArgument(boolean b, @Nullable String errorMessageTemplate, int p1, int p2)`	Ensures the truth of an expression involving one or more parameters to the calling method.
`static void`	`checkArgument(boolean b, @Nullable String errorMessageTemplate, int p1, long p2)`	Ensures the truth of an expression involving one or more parameters to the calling method.
`static void`	`checkArgument(boolean b, @Nullable String errorMessageTemplate, int p1, @Nullable Object p2)`	Ensures the truth of an expression involving one or more parameters to the calling method.
`static void`	`checkArgument(boolean b, @Nullable String errorMessageTemplate, long p1)`	Ensures the truth of an expression involving one or more parameters to the calling method.
`static void`	`checkArgument(boolean b, @Nullable String errorMessageTemplate, long p1, char p2)`	Ensures the truth of an expression involving one or more parameters to the calling method.
`static void`	`checkArgument(boolean b, @Nullable String errorMessageTemplate, long p1, int p2)`	Ensures the truth of an expression involving one or more parameters to the calling method.
`static void`	`checkArgument(boolean b, @Nullable String errorMessageTemplate, long p1, long p2)`	Ensures the truth of an expression involving one or more parameters to the calling method.
`static void`	`checkArgument(boolean b, @Nullable String errorMessageTemplate, long p1, @Nullable Object p2)`	Ensures the truth of an expression involving one or more parameters to the calling method.
`static void`	`checkArgument(boolean b, @Nullable String errorMessageTemplate, @Nullable Object p1)`	Ensures the truth of an expression involving one or more parameters to the calling method.
`static void`	`checkArgument(boolean expression, @Nullable String errorMessageTemplate, @Nullable Object @Nullable ... errorMessageArgs)`	Ensures the truth of an expression involving one or more parameters to the calling method.
`static void`	`checkArgument(boolean b, @Nullable String errorMessageTemplate, @Nullable Object p1, char p2)`	Ensures the truth of an expression involving one or more parameters to the calling method.
`static void`	`checkArgument(boolean b, @Nullable String errorMessageTemplate, @Nullable Object p1, int p2)`	Ensures the truth of an expression involving one or more parameters to the calling method.
`static void`	`checkArgument(boolean b, @Nullable String errorMessageTemplate, @Nullable Object p1, long p2)`	Ensures the truth of an expression involving one or more parameters to the calling method.
`static void`	`checkArgument(boolean b, @Nullable String errorMessageTemplate, @Nullable Object p1, @Nullable Object p2)`	Ensures the truth of an expression involving one or more parameters to the calling method.
`static void`	`checkArgument(boolean b, @Nullable String errorMessageTemplate, @Nullable Object p1, @Nullable Object p2, @Nullable Object p3)`	Ensures the truth of an expression involving one or more parameters to the calling method.
`static void`	`checkArgument(boolean b, @Nullable String errorMessageTemplate, @Nullable Object p1, @Nullable Object p2, @Nullable Object p3, @Nullable Object p4)`	Ensures the truth of an expression involving one or more parameters to the calling method.
`static int`	`checkElementIndex(int index, int size)`	Ensures that `index` specifies a valid element in an array, list or string of size `size`.
`static int`	`checkElementIndex(int index, int size, @Nullable String desc)`	Ensures that `index` specifies a valid element in an array, list or string of size `size`.
`static <T extends @NonNull Object> T`	`checkNotNull(T reference)`	Ensures that an object reference passed as a parameter to the calling method is not null.
`static <T extends @NonNull Object> T`	`checkNotNull(T reference, @Nullable Object errorMessage)`	Ensures that an object reference passed as a parameter to the calling method is not null.
`static <T extends @NonNull Object> T`	`checkNotNull(T obj, @Nullable String errorMessageTemplate, char p1)`	Ensures that an object reference passed as a parameter to the calling method is not null.
`static <T extends @NonNull Object> T`	`checkNotNull(T obj, @Nullable String errorMessageTemplate, char p1, char p2)`	Ensures that an object reference passed as a parameter to the calling method is not null.
`static <T extends @NonNull Object> T`	`checkNotNull(T obj, @Nullable String errorMessageTemplate, char p1, int p2)`	Ensures that an object reference passed as a parameter to the calling method is not null.
`static <T extends @NonNull Object> T`	`checkNotNull(T obj, @Nullable String errorMessageTemplate, char p1, long p2)`	Ensures that an object reference passed as a parameter to the calling method is not null.
`static <T extends @NonNull Object> T`	`checkNotNull(T obj, @Nullable String errorMessageTemplate, char p1, @Nullable Object p2)`	Ensures that an object reference passed as a parameter to the calling method is not null.
`static <T extends @NonNull Object> T`	`checkNotNull(T obj, @Nullable String errorMessageTemplate, int p1)`	Ensures that an object reference passed as a parameter to the calling method is not null.
`static <T extends @NonNull Object> T`	`checkNotNull(T obj, @Nullable String errorMessageTemplate, int p1, char p2)`	Ensures that an object reference passed as a parameter to the calling method is not null.
`static <T extends @NonNull Object> T`	`checkNotNull(T obj, @Nullable String errorMessageTemplate, int p1, int p2)`	Ensures that an object reference passed as a parameter to the calling method is not null.
`static <T extends @NonNull Object> T`	`checkNotNull(T obj, @Nullable String errorMessageTemplate, int p1, long p2)`	Ensures that an object reference passed as a parameter to the calling method is not null.
`static <T extends @NonNull Object> T`	`checkNotNull(T obj, @Nullable String errorMessageTemplate, int p1, @Nullable Object p2)`	Ensures that an object reference passed as a parameter to the calling method is not null.
`static <T extends @NonNull Object> T`	`checkNotNull(T obj, @Nullable String errorMessageTemplate, long p1)`	Ensures that an object reference passed as a parameter to the calling method is not null.
`static <T extends @NonNull Object> T`	`checkNotNull(T obj, @Nullable String errorMessageTemplate, long p1, char p2)`	Ensures that an object reference passed as a parameter to the calling method is not null.
`static <T extends @NonNull Object> T`	`checkNotNull(T obj, @Nullable String errorMessageTemplate, long p1, int p2)`	Ensures that an object reference passed as a parameter to the calling method is not null.
`static <T extends @NonNull Object> T`	`checkNotNull(T obj, @Nullable String errorMessageTemplate, long p1, long p2)`	Ensures that an object reference passed as a parameter to the calling method is not null.
`static <T extends @NonNull Object> T`	`checkNotNull(T obj, @Nullable String errorMessageTemplate, long p1, @Nullable Object p2)`	Ensures that an object reference passed as a parameter to the calling method is not null.
`static <T extends @NonNull Object> T`	`checkNotNull(T obj, @Nullable String errorMessageTemplate, @Nullable Object p1)`	Ensures that an object reference passed as a parameter to the calling method is not null.
`static <T extends @NonNull Object> T`	`checkNotNull(T reference, @Nullable String errorMessageTemplate, @Nullable Object @Nullable ... errorMessageArgs)`	Ensures that an object reference passed as a parameter to the calling method is not null.
`static <T extends @NonNull Object> T`	`checkNotNull(T obj, @Nullable String errorMessageTemplate, @Nullable Object p1, char p2)`	Ensures that an object reference passed as a parameter to the calling method is not null.
`static <T extends @NonNull Object> T`	`checkNotNull(T obj, @Nullable String errorMessageTemplate, @Nullable Object p1, int p2)`	Ensures that an object reference passed as a parameter to the calling method is not null.
`static <T extends @NonNull Object> T`	`checkNotNull(T obj, @Nullable String errorMessageTemplate, @Nullable Object p1, long p2)`	Ensures that an object reference passed as a parameter to the calling method is not null.
`static <T extends @NonNull Object> T`	`checkNotNull(T obj, @Nullable String errorMessageTemplate, @Nullable Object p1, @Nullable Object p2)`	Ensures that an object reference passed as a parameter to the calling method is not null.
`static <T extends @NonNull Object> T`	`checkNotNull(T obj, @Nullable String errorMessageTemplate, @Nullable Object p1, @Nullable Object p2, @Nullable Object p3)`	Ensures that an object reference passed as a parameter to the calling method is not null.
`static <T extends @NonNull Object> T`	`checkNotNull(T obj, @Nullable String errorMessageTemplate, @Nullable Object p1, @Nullable Object p2, @Nullable Object p3, @Nullable Object p4)`	Ensures that an object reference passed as a parameter to the calling method is not null.
`static int`	`checkPositionIndex(int index, int size)`	Ensures that `index` specifies a valid position in an array, list or string of size `size`.
`static int`	`checkPositionIndex(int index, int size, @Nullable String desc)`	Ensures that `index` specifies a valid position in an array, list or string of size `size`.
`static void`	`checkPositionIndexes(int start, int end, int size)`	Ensures that `start` and `end` specify valid positions in an array, list or string of size `size`, and are in order.
`static void`	`checkState(boolean expression)`	Ensures the truth of an expression involving the state of the calling instance, but not involving any parameters to the calling method.
`static void`	`checkState(boolean expression, @Nullable Object errorMessage)`	Ensures the truth of an expression involving the state of the calling instance, but not involving any parameters to the calling method.
`static void`	`checkState(boolean b, @Nullable String errorMessageTemplate, char p1)`	Ensures the truth of an expression involving the state of the calling instance, but not involving any parameters to the calling method.
`static void`	`checkState(boolean b, @Nullable String errorMessageTemplate, char p1, char p2)`	Ensures the truth of an expression involving the state of the calling instance, but not involving any parameters to the calling method.
`static void`	`checkState(boolean b, @Nullable String errorMessageTemplate, char p1, int p2)`	Ensures the truth of an expression involving the state of the calling instance, but not involving any parameters to the calling method.
`static void`	`checkState(boolean b, @Nullable String errorMessageTemplate, char p1, long p2)`	Ensures the truth of an expression involving the state of the calling instance, but not involving any parameters to the calling method.
`static void`	`checkState(boolean b, @Nullable String errorMessageTemplate, char p1, @Nullable Object p2)`	Ensures the truth of an expression involving the state of the calling instance, but not involving any parameters to the calling method.
`static void`	`checkState(boolean b, @Nullable String errorMessageTemplate, int p1)`	Ensures the truth of an expression involving the state of the calling instance, but not involving any parameters to the calling method.
`static void`	`checkState(boolean b, @Nullable String errorMessageTemplate, int p1, char p2)`	Ensures the truth of an expression involving the state of the calling instance, but not involving any parameters to the calling method.
`static void`	`checkState(boolean b, @Nullable String errorMessageTemplate, int p1, int p2)`	Ensures the truth of an expression involving the state of the calling instance, but not involving any parameters to the calling method.
`static void`	`checkState(boolean b, @Nullable String errorMessageTemplate, int p1, long p2)`	Ensures the truth of an expression involving the state of the calling instance, but not involving any parameters to the calling method.
`static void`	`checkState(boolean b, @Nullable String errorMessageTemplate, int p1, @Nullable Object p2)`	Ensures the truth of an expression involving the state of the calling instance, but not involving any parameters to the calling method.
`static void`	`checkState(boolean b, @Nullable String errorMessageTemplate, long p1)`	Ensures the truth of an expression involving the state of the calling instance, but not involving any parameters to the calling method.
`static void`	`checkState(boolean b, @Nullable String errorMessageTemplate, long p1, char p2)`	Ensures the truth of an expression involving the state of the calling instance, but not involving any parameters to the calling method.
`static void`	`checkState(boolean b, @Nullable String errorMessageTemplate, long p1, int p2)`	Ensures the truth of an expression involving the state of the calling instance, but not involving any parameters to the calling method.
`static void`	`checkState(boolean b, @Nullable String errorMessageTemplate, long p1, long p2)`	Ensures the truth of an expression involving the state of the calling instance, but not involving any parameters to the calling method.
`static void`	`checkState(boolean b, @Nullable String errorMessageTemplate, long p1, @Nullable Object p2)`	Ensures the truth of an expression involving the state of the calling instance, but not involving any parameters to the calling method.
`static void`	`checkState(boolean b, @Nullable String errorMessageTemplate, @Nullable Object p1)`	Ensures the truth of an expression involving the state of the calling instance, but not involving any parameters to the calling method.
`static void`	`checkState(boolean expression, @Nullable String errorMessageTemplate, @Nullable Object @Nullable ... errorMessageArgs)`	Ensures the truth of an expression involving the state of the calling instance, but not involving any parameters to the calling method.
`static void`	`checkState(boolean b, @Nullable String errorMessageTemplate, @Nullable Object p1, char p2)`	Ensures the truth of an expression involving the state of the calling instance, but not involving any parameters to the calling method.
`static void`	`checkState(boolean b, @Nullable String errorMessageTemplate, @Nullable Object p1, int p2)`	Ensures the truth of an expression involving the state of the calling instance, but not involving any parameters to the calling method.
`static void`	`checkState(boolean b, @Nullable String errorMessageTemplate, @Nullable Object p1, long p2)`	Ensures the truth of an expression involving the state of the calling instance, but not involving any parameters to the calling method.
`static void`	`checkState(boolean b, @Nullable String errorMessageTemplate, @Nullable Object p1, @Nullable Object p2)`	Ensures the truth of an expression involving the state of the calling instance, but not involving any parameters to the calling method.
`static void`	`checkState(boolean b, @Nullable String errorMessageTemplate, @Nullable Object p1, @Nullable Object p2, @Nullable Object p3)`	Ensures the truth of an expression involving the state of the calling instance, but not involving any parameters to the calling method.
`static void`	`checkState(boolean b, @Nullable String errorMessageTemplate, @Nullable Object p1, @Nullable Object p2, @Nullable Object p3, @Nullable Object p4)`	Ensures the truth of an expression involving the state of the calling instance, but not involving any 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

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:

IllegalArgumentException - if expression is false

checkArgument
```
public static void checkArgument(boolean expression,
                                 @Nullable 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:

IllegalArgumentException - if expression is false

checkArgument
```
public static void checkArgument(boolean expression,
                                 @Nullable String errorMessageTemplate,
                                 @Nullable Object @Nullable ... 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:

IllegalArgumentException - if expression is false