格林模拟试题二参考答案(2)
添加时间: 2007-9-22 6:44:27 作者: JAVA认证考试 阅读次数:35 来源: http://www.d9soft.com
Answer 23)
4) The class can only access final variables
Answer 24)
1) To call from the currently running thread to allow another thread of the same or higher priority to run
Option 3 looks plausible but there is no guarantee that the thread that grabs the cpu time will be of a higher priority. It will depend on the threading algorithm of the Java Virtual Machine and the underlying operating system
Answer 25)
4) Compilation and running with output 0 to 9
Answer 26)
1) None of these options
Because of the lack of a break statement after the break 10; statement the actual output will be
"ten" followed by "twenty"
Answer 27)
4) System.gc();
Answer 28)
1) Compilation succeeds and at run time an output of 0 and false
The default value for a boolean declared at class level is false, and integer is 0;
Answer 29)
1) Compile time error
You will get an error saying something like "Cant make a static reference to a non static variable". Note that the main method is static. Even if main was not static the array argv is local to the main method and would thus not be visible within amethod.
Answer 30)
3) Output of "Not equal"
Despite the actual character strings matching, using the == operator will simply compare memory location. Because the one string was created with the new operator it will be in a different location in memory to the other string.
Answer 31)
4) Compile and run with output of "Pausing" and "Continuing" after a key is hit
An overriden method in a sub class must not throw Exceptions not thrown in the base class. In the case of the method amethod it throws no exceptions and will thus compile without complain. There is no reason that a constructor cannot be protected.
Answer 32)
4) Compile time error because of the line creating the instance of Inner
This looks like a question about inner classes but it is also a reference to the fact that the main method is static and thus you cannot directly access a non static method. The line causing the error could be fixed by changing it to say
Inner i = new Outer().new Inner();Then the code would compile and run producing the output "Inner"
Answer 33)
1) Error at compile time
If you implement an interface you must create bodies for all methods in that interface. This code will produce an error saying that MyWc must be declared abstract because it does not define all of the methods in WindowListener. Option 4 is nonsense as comments can appear anywhere. Option 3 suggesting that it might compile but not produce output is ment to mislead on the basis that what looks like a constructor is actually an ordinary method as it has a return type.
Answer 34)
4) Compile time error
An error will be caused by attempting to define an integer as static within a method. The lifetime of a field within a method is the duration of the running of the method. A static field exists once only for the class. An approach like this does work with Visual Basic.
Answer 35)
4)int z = 015;
The letters c and s do not exist as literal indicators and a String must be enclosed with double quotes, not single as in this case.
Answer 36)
1)double
4)instanceof
Note the upper case S on switch means it is not a keyword and the word then is part of Visual Basic but not Java . Also, instanceof looks like a method but is actually a keyword,
Answer 37)
4) -3.0
Answer 38)
3) one
Command line parameters start from 0 and from the first parameter after the name of the compile (normally Java )
Answer 39)
4) The Set is designed for unique elements.
Collection is an interface, not a class. The Collection interface includes a method called iterator. This returns an instance of the Iterator class which has some similarities with Enumerators.
The name set should give away the purpose of the Set interface as it is analogous to the Set concept in relational databases which implies uniquness.
Answer 40)
2) If multiple listeners are added to a component the events will be processed for all but with no guarantee in the order
4) You may remove as well add listeners to a component.
It ought to be fairly intuitive that a component ought to be able to have multiple listeners. After all, a text field might want to respond to both the mouse and keyboard
Answer 41)
1) b=m;
3) d =i;
You can assign up the inheritance tree from a child to a parent but not the other way without an explicit casting. A boolean can only ever be assigned a boolean value.
Answer 42)
2) You can obtain a mutually exclusive lock on any object
3) A thread can obtain a mutually exclusive lock on an object by calling a synchronized method on that object.
4) Thread scheduling algorithms are platform dependent
Yes that says dependent and not independent.
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