Class Preconditions

Method Details

• checkArgument

  public static void checkArgument(boolean expression, String message)

  Checks the truth of the given expression and throws a customized IllegalArgumentException if it is false. Intended for doing parameter validation in methods and constructors, e.g.:

   public void foo(int count) {
      Preconditions.checkArgument(count > 0, "count must be positive.");
   }
   

  Parameters:

  expression - the precondition to check involving one ore more parameters to the calling method or constructor

  message - the detail message to be used in the event that an exception is thrown

  Throws:

  IllegalArgumentException - if expression is false

• checkArgument

  public static void checkArgument(boolean expression, String messageFormat, Object... messageArgs)

  Checks the truth of the given expression and throws a customized IllegalArgumentException if it is false. Intended for doing parameter validation in methods and constructors, e.g.:

   public void foo(int count) {
      Preconditions.checkArgument(count > 0, "count must be positive: %s.", count);
   }
   

  Parameters:

  expression - the precondition to check involving one ore more parameters to the calling method or constructor

  messageFormat - a format string for the detail message to be used in the event that an exception is thrown.

  messageArgs - the arguments referenced by the format specifiers in the messageFormat

  Throws:

  IllegalArgumentException - if expression is false

• checkNotNull

  public static <T> T checkNotNull(T reference, String message)

  Checks that the given object reference is not null and throws a customized NullPointerException if it is. Intended for doing parameter validation in methods and constructors, e.g.:

   public void foo(Bar bar, Baz baz) {
        this.bar = Preconditions.checkNotNull(bar, "bar must not be null.");
        Preconditions.checkNotBull(baz, "baz must not be null.");
   }
   

  Type Parameters:

  T - the type of the reference

  Parameters:

  reference - the object reference to check for being null

  message - the detail message to be used in the event that an exception is thrown

  Returns:

  reference if not null

  Throws:

  NullPointerException - if reference is null

• checkNotNull

  public static <T> T checkNotNull(T reference, String messageFormat, Object... messageArgs)

  Checks that the given object reference is not null and throws a customized NullPointerException if it is. Intended for doing parameter validation in methods and constructors, e.g.:

   public void foo(Bar bar, Baz baz) {
        this.bar = Preconditions.checkNotNull(bar, "bar must not be null.");
        Preconditions.checkNotBull(baz, "The %s must not be null.", "baz");
   }
   

  Type Parameters:

  T - the type of the reference

  Parameters:

  reference - the object reference to check for being null

  messageFormat - a format string for the detail message to be used in the event that an exception is thrown.

  messageArgs - the arguments referenced by the format specifiers in the messageFormat

  Returns:

  reference if not null

  Throws:

  NullPointerException - if reference is null

• checkState

  public static void checkState(boolean expression, String message)

  Checks the truth of the given expression and throws a customized IllegalStateException if it is false. Intended for doing validation in methods involving the state of the calling instance, but not involving parameters of the calling method, e.g.:

   public void unlock() {
      Preconditions.checkState(locked, "Must be locked to be unlocked.");
   }
   

  Parameters:

  expression - the precondition to check involving the state of the calling instance

  message - the detail message to be used in the event that an exception is thrown

  Throws:

  IllegalStateException - if expression is false

• checkState

  public static void checkState(boolean expression, String messageFormat, Object... messageArgs)

  Checks the truth of the given expression and throws a customized IllegalStateException if it is false. Intended for doing validation in methods involving the state of the calling instance, but not involving parameters of the calling method, e.g.:

   public void unlock() {
      Preconditions.checkState(locked,
          "Must be locked to be unlocked. Most recent lock: %s",
          mostRecentLock);
   }
   

  Parameters:

  expression - the precondition to check involving the state of the calling instance

  messageFormat - a format string for the detail message to be used in the event that an exception is thrown.

  messageArgs - the arguments referenced by the format specifiers in the messageFormat

  Throws:

  IllegalStateException - if expression is false

• checkNotBlank

  public static String checkNotBlank(String str, String message)

  Checks that the given string is not blank and throws a customized NullPointerException if it is null, and a customized IllegalArgumentException if it is empty or whitespace. Intended for doing parameter validation in methods and constructors, e.g.:

   public void foo(String text) {
        checkNotBlank(text, "The text must not be null, empty or whitespace.");
   }
   

  Parameters:

  str - the string to check for being blank

  message - the detail message to be used in the event that an exception is thrown

  Returns:

  str if not null

  Throws:

  NullPointerException - if str is null

  IllegalArgumentException - if str is empty or whitespace

• checkNotBlank

  public static String checkNotBlank(String str, String messageFormat, Object... messageArgs)

  Checks that the given string is not blank and throws a customized NullPointerException if it is null, and a customized IllegalArgumentException if it is empty or whitespace. Intended for doing parameter validation in methods and constructors, e.g.:

   public void foo(String text, String id) {
        checkNotBlank(
            text,
            "The text for %s must not be null, empty or whitespace.",
            id);
   }
   

  Parameters:

  str - the string to check for being blank

  messageFormat - a format string for the detail message to be used in the event that an exception is thrown.

  messageArgs - the arguments referenced by the format specifiers in the messageFormat

  Returns:

  str if not null

  Throws:

  NullPointerException - if str is null

  IllegalArgumentException - if str is empty or whitespace