Language Fundamentals Questions

• Java — In an interface, which explicit declarations are equivalent to the implicit constant defined on line 3? Given: public interface Foo { int k = 4; // Line 3 } Pick the three equivalent explicit forms.
• Java — Which declarations are valid inside an interface definition?
• Java — Which one is a valid boolean variable declaration and initialization?
• Java — What is the numerical range of a char (primitive type)?
• In Java programming, which of the following is a valid declaration of a String variable?
• Which of the following is a valid Java keyword (reserved word) recognized by the Java compiler?
• In Java, which option both declares an int array and initializes it immediately with five specific numbers?
• In Java, which three are valid declarations for a float variable among the following candidates?
• Which of the following is a reserved Java keyword (cannot be used as an identifier)?
• In Java, which three of the following are valid char declarations or assignments?
• Java arrays default values: which four entries correctly describe default element values for the given types?
• Which one of the following lists contains only valid Java language keywords (no identifiers or non-Java tokens)?
• In Java, which three are legal array declarations among the following?
• Which statement legally declares, constructs, and initializes a one-dimensional int array in Java?
• Java arrays and command-line arguments: trace the output when copying args into a 2D array reference. public class CommandArgsThree { public static void main(String[] args) { String[][] argCopy = new String[2][2]; int x; argCopy[0] = args; // first row refers to args array x = argCopy[0].length; for (int y = 0; y < x; y++) { System.out.print(" " + argCopy[0][y]); } } } // Invocation: > java CommandArgsThree 1 2 3
• Java arrays and command-line arguments: populating a larger array from args and printing names[2]. public class X { public static void main(String[] args) { String[] names = new String[5]; for (int x = 0; x < args.length; x++) names[x] = args[x]; System.out.println(names[2]); } } // Invocation: > java X a b
• Java entry point rules: what happens when main is not declared static? public class F0091 { public void main(String[] args) { System.out.println("Hello" + args[0]); } } // Command line: > java F0091 world
• Java command-line arguments and array bounds: trace the loop and identify the runtime behavior. public class CommandArgsTwo { public static void main(String[] argh) { int x; x = argh.length; // number of arguments for (int y = 1; y <= x; y++) { System.out.print(" " + argh[y]); // note: starts at 1 and uses <= } } } // Invocation: > java CommandArgsTwo 1 2 3
• Java multidimensional arrays (jagged): accessing an uninitialized inner array element. public class TestDogs { public static void main(String[] args) { Dog[][] theDogs = new Dog[3][]; // only outer dimension allocated System.out.println(theDogs[2][0].toString()); } } class Dog { }
• Java keywords and for-loop tracing: identify the compile-time outcome of using “signed”. public class Test { public static void main(String[] args) { signed int x = 10; for (int y = 0; y < 5; y++, x--) System.out.print(x + ", "); } }