Immutable objects in Java: Allow modifications on their content Do not allow modifications on their content Can be cloned without restrictions Support dynamic memory allocation
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Immutable objects are objects whose state cannot be modified after they are created. Show more…
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Problem 4: Our Rectangle class revisited Recall the Rectangle class that we defined in lecture. (The relevant version of this class is available here.) Consider a potential non-static method named rotate that would rotate a Rectangle object 90 degrees by swapping its width and height values. For example, if a Rectangle's dimensions are 10 x 30, then calling the rotate method would change its dimensions to 30 x 10. Because the method only needs to change the internals of the called object, it doesn't need to – and should not! – return a value. What type of instance method would rotate be, an accessor or mutator? Give an appropriate method header for this method, making sure to take into account the fact that the method is non-static. You do not need to define the body of the method. Now consider a potential non-static method named largerThan that takes another Rectangle object and determines if the called Rectangle object (i.e., the one on which the method is invoked) has a larger area than the other Rectangle object – returning true if the called object has a larger area and false otherwise. What type of instance method would largerThan be, an accessor or mutator? Give an appropriate method header for this method, making sure to take into account the fact that the method is non-static. You do not need to define the body of the method. Consider the following client code — i.e., code from another class that uses a Rectangle object: Rectangle r1 = new Rectangle(60, 80); System.out.println("r1's height is: " + r1.height); r1.width = r1.width + 20; System.out.println(r1); // print the new dimensions Because our Rectangle class employs appropriate encapsulation, this code fragment will not compile. Explain what problems are present in the code fragment that prevent it from compiling. Rewrite the fragment to eliminate those problems while maintaining the intended functionality of the original version. Don't make any unnecessary changes.
Akash M.
Is it possible to change an object's momentum without changing its kinetic energy? What about the reverse situation?
31. Which two are limitations of an array of primitives (i.e., int[] x)? - You can create only one array in a class. - You cannot overwrite the contents of an array once initialized. - The size of the array is fixed during array creation and cannot grow once initialized. - You need to create your own methods to manipulate array contents. 32. Which two cannot be stored in an ArrayList? - int - float - Integer - String 33. Runtime errors can be caught by Java's exception handling mechanism. - True - False 34. What are two disadvantages of adding print statements for debugging? - Print statements cannot print the values of variables. - It's tedious to remove print statements. - Too many print statements lead to information overload. - Print statements cannot print the values of an object's fields. 35. Using the NetBeans debugger, you can set breakpoints and trace through a program one line at a time. - True - False
Madhur L.
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