SCJP认证试题(八)

 /**
 *
 * @author yaoyuan
 */

11	public static void test(String str){
12		if(str == null | str.length() ==){
13			System.out.println("String is empty");
14		}else{
15			System.out.println("String is not empty");
16		}
17	}

And the invocation:
31 test(null);
what is the result?

A An exception is thrown at runtime
B "String is empty" is printed to output
C Compilation fails because of an error in line 12
D "String is not empty" is printed to output



Answer  : A

 /**
 *
 * @author yaoyuan
 */

15	public class Yippee{
16		public static void main(String[] args){
17			for(int x=1;x<args.length;x++){
18				System.out.println(args[x] + " ");
19			}
20		}
21	}

and two separate command line invocations:

java Yippee
java Yippee 1 2 3 4

What is the result?

A No output is produced
1 2 3
B No output is produced
2 3 4
C No output is produced
1 2 3 4
D An exception is thrown runtime
1 2 3
E An exception is thrown runtime
2 3 4
F An exception is thrown runtime
1 2 3 4


Answer  : B

 /**
 *
 * @author yaoyuan
 */


13	public class Pass{
14		public static void main(String[] args){
15			int x = 5;
16			Pass p = new Pass();
17			p.doStuff(x);
18			System.out.println("main x = " + x);
19		}
20		
21		void doStuff(int x){
22			System.out.print("doStuff x=" + x++);
23		}
24	}

What is the result?


A Compilation fails
B An exception is thrown at runtime
C doStuff x=6 main x =6
D doStuff x=5 main x =5
E doStuff x=5 main x =6
F doStuff x=6 main x =5


Answer : D

 /**
 *
 * @author yaoyuan
 */


11	class A{
12		public void process(){System.out.print("A");}}
13	class B extends A{
14		public void process() throw IOException{
15			super.process();
16			System.out.print("B");
17			throw new IOException();
18	}}
19	public static void main(String[] args){
20		try{new B().process();}
21		catch(IOException e){System.out.println("Exception");}}

What is the result?


A Exception
B A,B,Exception
C Compilation fails because of an error in line 20
D Compilation fails because of an error in line 14
E A NullPointerException is thrown at runtime



Answer : D

 /**
 *
 * @author yaoyuan
 */

public class Test{
	public enum Dogs{collie,harrier,shepherd};
	public static void main(String[] args){
		Dogs myDog = Dogs.shepherd;
		switch(myDog){
			case collie:
				System.out.print("collie");
			case default:
				System.out.print("retriever");
			case harrier:
				System.out.print("harrier");
		}
	}
}

What is the result?

A harrier
B shepherd
C retriever
D Compilation fails
E retriever harrier
F An exception is thrown at runtime


Answer: D

 /**
 *
 * @author yaoyuan
 */

public static Collection get(){
	Collection sorted = new LinkedList();
	sorted.add("B");
	sorted.add("C");
	sorted.add("A");
	return sorted;
}

public static void main(String[] args){
	for(Object obj:get()){
		System.out.print(obj + ", ");
	}
}

What is the result?


A A,B,C
B B,C,A
C Compilation fails
D The code runs with no output
E An exception is thrown at runtime



Answer: B

 /**
 *
 * @author yaoyuan
 */


static void test() throws Error{
	if(true) throw new AssertionError();
	System.out.print("test");
}

public static void main(String[] args){
	try{test();}
	catch(Exception ex){System.out.print("exception");}
	System.out.println("end");
}

What is the result?


A end
B Compilation fails
C exception end
D exception test end
E A Throwable is thrown by main
F A Exception is thrown by main


Answer : E

 /**
 *
 * @author yaoyuan
 */


Float pi = new Float(3.14f);
if(pi > 3){
	System.out.print("pi is bigger than 3.");
}
else{
	System.out.print("pi is not bigger than 3");
}
finally{
	System.out.print("Have a nice day.");
}

What is the result?


A Compilation fails
B pi is bigger than 3
C An exception occurs at runtime
D pi is bigger than 3.Have a nice day.
E pi is not bigger than 3.Have a nice day.



Answer:A

 /**
 *
 * @author yaoyuan
 */

10	interface Foo{}
11	class Alpha implements Alpha{}
12	class Beta extends Beta{}
13	class Delta extends Beta{
14		public static void main(String[] args){
15			Beta x= new Beta();
16			//insert code here
17		}
18	}

Which code, inserted at line 16 will cause a java.lang.ClassCaseException?


A Alpha a = x;
B Foo f = (Delta)x;
C Foo f = (Alpha)x;
D Beta b = (Beta)(Alpha)x;


Answer : B



/**
*
* @author yaoyuan
*/


Given a method that must ensure that its parameter is not null:

11	public void someMethod(Object value)
12		//check for null value
.............
20	System.out.println(value.getClass());
21	}

What inserted at line 12 is the appropriate way to handle a null value?


A assert value == null;
B assert value != null,"value is null";
C if(value == null){
throw new AssertionException("value is null");
}
D if(value == null){
throw new IllegalArgumentException("value is null");
}


Answer : D

不错，可是貌似都做过曾经

前几天，有几个哥们做，我就看了一下，挺不错的，有时间就整理一下........

我郁闷，不实际运行的话，都会做错。

看完，感受：
革命尚未成功
同志还需努力

麻烦帅哥你放题目时候还是要态度认真一点，你看你第一道题，的第一个判断子式是if(str == null | str.length() ==)，虽然应该能想到是str.length==0,但是你打的时候也注意点撒，还有，null后面是只有一个“|”还是你少输入一个？