Final answer:
The 'gainAlt()' and 'loseAlt()' methods in Java for airplane control would typically be used to increase and decrease the aircraft's altitude, respectively. They are called on an instance of the Airplane class to alter its altitude.
Step-by-step explanation:
The gainAlt() and loseAlt() functions within the context of airplane control in Java are likely to be methods that manage the altitude of the aircraft. When these methods are part of an Airplane class, gainAlt() would typically increase the altitude of the airplane, whereas loseAlt() would decrease it. To use these methods, you would have an instance of the Airplane class, and you would call these methods on that instance.
For example:
Airplane myPlane = new Airplane();
myPlane.gainAlt(); // This would increase the plane's altitude
myPlane.loseAlt(); // This would decrease the plane's altitude
It's important to note that while these are common functionalities, the exact way the methods work would depend on how they are implemented in the code.