Class IllegalStateException. Signals that a method has been invoked at an illegal or inappropriate time. In other words, the Java environment or Java application is not in an appropriate state for the requested operation.

When should you throw IllegalStateException?

Another commonly reused exception is IllegalStateException. This is generally the exception to throw if the invocation is illegal because of the state of the receiving object. For example, this would be the exception to throw if the caller attempted to use some object before it had been properly initialized.

What is an IllegalStateException?

Added in API level 1. public IllegalStateException (String message, Throwable cause) Constructs a new exception with the specified detail message and cause. Note that the detail message associated with cause is not automatically incorporated in this exception's detail message.