Preconditions (Guava: Google Core Libraries for Java 20.0 API)

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 (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 root
   }

   void 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.
Warning about performance

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);
   }
```
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.
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

In Preconditions error message template strings, only the "%s" specifier is supported, not the full range of Formatter specifiers.
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 and 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, Object errorMessage)` Ensures the truth of an expression involving one or more parameters to the calling method.
`static void`	`checkArgument(boolean b, String errorMessageTemplate, char p1)` Ensures the truth of an expression involving one or more parameters to the calling method.
`static void`	`checkArgument(boolean b, 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, 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, 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, String errorMessageTemplate, char p1, Object p2)` Ensures the truth of an expression involving one or more parameters to the calling method.
`static void`	`checkArgument(boolean b, String errorMessageTemplate, int p1)` Ensures the truth of an expression involving one or more parameters to the calling method.
`static void`	`checkArgument(boolean b, 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, 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, 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, String errorMessageTemplate, int p1, Object p2)` Ensures the truth of an expression involving one or more parameters to the calling method.
`static void`	`checkArgument(boolean b, String errorMessageTemplate, long p1)` Ensures the truth of an expression involving one or more parameters to the calling method.
`static void`	`checkArgument(boolean b, 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, 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, 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, String errorMessageTemplate, long p1, Object p2)` Ensures the truth of an expression involving one or more parameters to the calling method.
`static void`	`checkArgument(boolean expression, String errorMessageTemplate, Object... errorMessageArgs)` Ensures the truth of an expression involving one or more parameters to the calling method.
`static void`	`checkArgument(boolean b, String errorMessageTemplate, Object p1)` Ensures the truth of an expression involving one or more parameters to the calling method.
`static void`	`checkArgument(boolean b, String errorMessageTemplate, Object p1, char p2)` Ensures the truth of an expression involving one or more parameters to the calling method.
`static void`	`checkArgument(boolean b, String errorMessageTemplate, Object p1, int p2)` Ensures the truth of an expression involving one or more parameters to the calling method.
`static void`	`checkArgument(boolean b, String errorMessageTemplate, Object p1, long p2)` Ensures the truth of an expression involving one or more parameters to the calling method.
`static void`	`checkArgument(boolean b, String errorMessageTemplate, Object p1, Object p2)` Ensures the truth of an expression involving one or more parameters to the calling method.
`static void`	`checkArgument(boolean b, String errorMessageTemplate, Object p1, Object p2, Object p3)` Ensures the truth of an expression involving one or more parameters to the calling method.
`static void`	`checkArgument(boolean b, String errorMessageTemplate, Object p1, Object p2, Object p3, 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, String desc)` Ensures that `index` specifies a valid element in an array, list or string of size `size`.
`static <T> T`	`checkNotNull(T reference)` Ensures that an object reference passed as a parameter to the calling method is not null.
`static <T> T`	`checkNotNull(T reference, Object errorMessage)` Ensures that an object reference passed as a parameter to the calling method is not null.
`static <T> T`	`checkNotNull(T obj, String errorMessageTemplate, char p1)` Ensures that an object reference passed as a parameter to the calling method is not null.
`static <T> T`	`checkNotNull(T obj, String errorMessageTemplate, char p1, char p2)` Ensures that an object reference passed as a parameter to the calling method is not null.
`static <T> T`	`checkNotNull(T obj, String errorMessageTemplate, char p1, int p2)` Ensures that an object reference passed as a parameter to the calling method is not null.
`static <T> T`	`checkNotNull(T obj, String errorMessageTemplate, char p1, long p2)` Ensures that an object reference passed as a parameter to the calling method is not null.
`static <T> T`	`checkNotNull(T obj, String errorMessageTemplate, char p1, Object p2)` Ensures that an object reference passed as a parameter to the calling method is not null.
`static <T> T`	`checkNotNull(T obj, String errorMessageTemplate, int p1)` Ensures that an object reference passed as a parameter to the calling method is not null.
`static <T> T`	`checkNotNull(T obj, String errorMessageTemplate, int p1, char p2)` Ensures that an object reference passed as a parameter to the calling method is not null.
`static <T> T`	`checkNotNull(T obj, String errorMessageTemplate, int p1, int p2)` Ensures that an object reference passed as a parameter to the calling method is not null.
`static <T> T`	`checkNotNull(T obj, String errorMessageTemplate, int p1, long p2)` Ensures that an object reference passed as a parameter to the calling method is not null.
`static <T> T`	`checkNotNull(T obj, String errorMessageTemplate, int p1, Object p2)` Ensures that an object reference passed as a parameter to the calling method is not null.
`static <T> T`	`checkNotNull(T obj, String errorMessageTemplate, long p1)` Ensures that an object reference passed as a parameter to the calling method is not null.
`static <T> T`	`checkNotNull(T obj, String errorMessageTemplate, long p1, char p2)` Ensures that an object reference passed as a parameter to the calling method is not null.
`static <T> T`	`checkNotNull(T obj, String errorMessageTemplate, long p1, int p2)` Ensures that an object reference passed as a parameter to the calling method is not null.
`static <T> T`	`checkNotNull(T obj, String errorMessageTemplate, long p1, long p2)` Ensures that an object reference passed as a parameter to the calling method is not null.
`static <T> T`	`checkNotNull(T obj, String errorMessageTemplate, long p1, Object p2)` Ensures that an object reference passed as a parameter to the calling method is not null.
`static <T> T`	`checkNotNull(T reference, String errorMessageTemplate, Object... errorMessageArgs)` Ensures that an object reference passed as a parameter to the calling method is not null.
`static <T> T`	`checkNotNull(T obj, String errorMessageTemplate, Object p1)` Ensures that an object reference passed as a parameter to the calling method is not null.
`static <T> T`	`checkNotNull(T obj, String errorMessageTemplate, Object p1, char p2)` Ensures that an object reference passed as a parameter to the calling method is not null.
`static <T> T`	`checkNotNull(T obj, String errorMessageTemplate, Object p1, int p2)` Ensures that an object reference passed as a parameter to the calling method is not null.
`static <T> T`	`checkNotNull(T obj, String errorMessageTemplate, Object p1, long p2)` Ensures that an object reference passed as a parameter to the calling method is not null.
`static <T> T`	`checkNotNull(T obj, String errorMessageTemplate, Object p1, Object p2)` Ensures that an object reference passed as a parameter to the calling method is not null.
`static <T> T`	`checkNotNull(T obj, String errorMessageTemplate, Object p1, Object p2, Object p3)` Ensures that an object reference passed as a parameter to the calling method is not null.
`static <T> T`	`checkNotNull(T obj, String errorMessageTemplate, Object p1, Object p2, Object p3, 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, 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 a 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, 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, 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, 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, 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, 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, String errorMessageTemplate, char p1, 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, 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, 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, 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, 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, String errorMessageTemplate, int p1, 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, 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, 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, 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, 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, String errorMessageTemplate, long p1, 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 expression, String errorMessageTemplate, Object... 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, String errorMessageTemplate, 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 b, String errorMessageTemplate, 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, String errorMessageTemplate, 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, String errorMessageTemplate, 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, String errorMessageTemplate, Object p1, 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, String errorMessageTemplate, Object p1, Object p2, 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, String errorMessageTemplate, Object p1, Object p2, Object p3, 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... 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

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