public class WrapTest { public static void main(String [] args) { int result = 0; short s = 42; Long x = new Long("42"); Long y = new Long(42); Short z = new Short("42"); Short x2 = new Short(s); Integer y2 = new Integer("42"); Integer z2 = new Integer(42); if (x == y) /* Line 13 */ result = 1; if (x.equals(y) ) /* Line 15 */ result = result + 10; if (x.equals(z) ) /* Line 17 */ result = result + 100; if (x.equals(x2) ) /* Line 19 */ result = result + 1000; if (x.equals(z2) ) /* Line 21 */ result = result + 10000; System.out.println("result = " + result); } }
Option B is incorrect because to call wait(), the thread must own the lock on the object that wait() is being invoked on, not the other way around.
Option C is wrong because notify() is defined in java.lang.Object.
Option D is wrong because notify() will not cause a thread to release its locks. The thread can only release its locks by exiting the synchronized code.
class Test1 { public int value; public int hashCode() { return 42; } } class Test2 { public int value; public int hashcode() { return (int)(value^5); } }
Option A and D are incorrect because these classes are legal.
Option B is incorrect based on the logic described above.
x = 0; if (x1.hashCode() != x2.hashCode() ) x = x + 1; if (x3.equals(x4) ) x = x + 10; if (!x5.equals(x6) ) x = x + 100; if (x7.hashCode() == x8.hashCode() ) x = x + 1000; System.out.println("x = " + x);
Option A is incorrect because if the hashCode() values are not equal, the two objects must not be equal.
Option C is incorrect because if equals() is not true there is no guarantee of any result from hashCode().
Option D is incorrect because hashCode() will often return == even if the two objects do not evaluate to equals() being true.
class Test { public static void main(String [] args) { printAll(args); } public static void printAll(String[] lines) { for(int i = 0; i < lines.length; i++) { System.out.println(lines[i]); Thread.currentThread().sleep(1000); } } }
A is incorrect, but it would be correct if the InterruptedException was dealt with.
B is incorrect, but it would still be incorrect if the InterruptedException was dealt with because all Java code, including the main() method, runs in threads.
C is incorrect. The sleep() method is static, so even if it is called on an instance, it still always affects the currently executing thread.
public class MyProgram { public static void throwit() { throw new RuntimeException(); } public static void main(String args[]) { try { System.out.println("Hello world "); throwit(); System.out.println("Done with try block "); } finally { System.out.println("Finally executing "); } } }
interface Base { boolean m1 (); byte m2(short s); }
(1) is incorrect because interfaces don't implement anything. (2) is incorrect because classes don't extend interfaces. (5) is incorrect because interface methods are implicitly public, so the methods being implemented must be public.
public class MyOuter { public static class MyInner { public static void foo() { } } }
MyOuter.MyInner mi = m.new MyOuter.MyInner();
Option B is incorrect because it doesn't use the enclosing name in the new.
Option C is incorrect because it uses incorrect syntax. When you instantiate a nested class by invoking new on an instance of the enclosing class, you do not use the enclosing name. The difference between Option A and C is that Option C is calling new on an instance of the enclosing class rather than just new by itself.
Option D is incorrect because it doesn't use the enclosing class name in the variable declaration.
> java F0091 world
public class F0091 { public void main( String[] args ) { System.out.println( "Hello" + args[0] ); } }
Exception in thread "main" java.lang.NoSuchMethodError: main
The Java Language Specification clearly states: "The main method must be declared public, static, and void. It must accept a single argument that is an array of strings."
class Bar { } class Test { Bar doBar() { Bar b = new Bar(); /* Line 6 */ return b; /* Line 7 */ } public static void main (String args[]) { Test t = new Test(); /* Line 11 */ Bar newBar = t.doBar(); /* Line 12 */ System.out.println("newBar"); newBar = new Bar(); /* Line 14 */ System.out.println("finishing"); /* Line 15 */ } }
Option A is wrong. This actually protects the object from garbage collection.
Option C is wrong. Because the reference in the doBar() method is returned on line 7 and is stored in newBar on line 12. This preserver the object created on line 6.
Option D is wrong. Not applicable because the object is eligible for garbage collection after line 14.
public class ExceptionTest { class TestException extends Exception {} public void runTest() throws TestException {} public void test() /* Point X */ { runTest(); } }
Option A is wrong. If you compile the code as given the compiler will complain:
"unreported exception must be caught or declared to be thrown" The class extends Exception so we are forced to test for exceptions.
Option C is wrong. The catch statement belongs in a method body not a method specification.
Option D is wrong. TestException is a subclass of Exception therefore the test method, in this example, must throw TestException or some other class further up the Exception tree. Throwing RuntimeException is just not on as this belongs in the java.lang.RuntimeException branch (it is not a superclass of TestException). The compiler complains with the same error as in A above.
Comments
There are no comments.Copyright ©CuriousTab. All rights reserved.