SCJP认证试题(六)

 /**
 *
 * @author yaoyuan
 */
public class A{
	public void method1(){
		B b = new B();
		b.method2();
5		//more code here
	}
}

public class B{
	public void method2(){
		C c = new C();
		c.method3();
5		//more code here
	}
}

public class C{
	public void method3(){
		//more code here	
	}

}

try{
	A a = new A();
27	a.methor1();
}
catch(Exception e){
29	System.out.print("an error occurred");
}

/**
*Which two statements are true if a NullPointerException is thrown on line 13 of class C?(choose two)
*
*
*A The application will crash
*B The code on line 29 will be executed
*C The code on line 5 of class A will execute
*D The code on line 5 of class B will execute
*E The exception will be propagated back to line 27
*/

[color=red]// Answer : B E[/color]

 /**
 *
 * @author yaoyuan
 */
25	int x = 12;
26	while(x < 10){
27		x--;
28	}
29	System.out.print(x);

/**
*What is the result?
*
*
*A 0
*B 10
*C 12
*D Line 29 will never be reached
*/

[color=red]// Answer : C[/color]

 /**
 *
 * @author yaoyuan
 */

1 public class CertKiller2{
2	Integer I;
3	int x;
4	
5	public CertKiller2(int y){
6		x = I + y;
7		System.out.println(x);
8	}
9
10	public static void main(String[] args){
11		new CertKiller2(new Integer(4));
12	}
13 }

/**
*What is the result?
*
*
*A The value "4" is printed at the command line
*B Compilation fails because of an error in line 6
*C Compilation fails because of an error in line 11
*D A NullPointerException occursatruntime
*E A NumberForm at Exception occursatruntime
*F An IllegalStateException occursatruntime
*/

[color=red]// Answer : D[/color]

 /**
 *
 * @author yaoyuan
 */
1	public static Iterator reverse(List list){
2		Collections.reverse(list);
3		return list.iterator();
4	}
5	public static void main(String[] args){
6		List list = new ArrayList();
7		list.add("1");list.add("2");list.add("3");
8		for(Object obj; reverse(list))
9			System.out.print(obj + ", ");
10	}

/**
*What is the result?
*
*
*A 3,2,1
*B 1,2,3
*C Compilation fails
*D The code runs with no output
*E An exception is thrown at runtime
*/

[color=red]// Answer : C[/color]

 /**
 *
 * @author yaoyuan
 */

11	public void testIfA(){
12		if(testIfB("true")){	
13			System.out.println("True");
14		}else{
15			System.out.println("Not true");
16		}
17	}
18	public Boolean testIfB(String str){
19		return Boolean.valueof(str);
20

/**
*What is the result when method testIfA is invoked?
*
*
*A True
*B Not true
*C An exception is thrown at runtime
*D Compilation fails because of an error at line 12
*E Compilation fails because of an error at line 19
*/

[color=red]// Answer : A[/color]

 /**
 *
 * @author yaoyuan
 */

23	int z = 5;
24	
25	public void CertKiller1(int x){
26		assert(x > 0);
27		switch(x){
28			case 2 x=3;
29			default; assert false; }}
30	
31		private void CertKiller2(int y){assert(y < 0);}
32		
33		private void CertKiller4(){assert(CertKiller4());}
34
35		private Boolean CertKiller4(){z = 6; return false;}

/**
*Which statement is true?
*
*
*A All of the assert statements are used appropriately
*B Only the assert statements line 31 is used appropriately
*C The assert statements on lines 29 and 31 are used appropriately
*D The assert statements on lines 26 and 29 are used appropriately
*E The assert statements on lines 29 and 33 are used appropriately
*F The assert statements on lines 29 ,31 and 33 are used appropriately
*G The assert statements on lines 26, 29 and 31 are used appropriately
*/

[color=red]// Answer : C[/color]

 /**
 *
 * @author yaoyuan
 */

11	public static void main(String[] args){
12		String str = "null";
13		if(str == null){
14			System.out.println("null");
15		}else(str.length() == 0){
16			System.out.println("zero");
17		}else{
18			System.out.println("some");
19		}
20	}

/**
*What is the result?
*
*
*A null
*B zero
*C some
*D Compilation fails
*E An exception is thrown at runtime
*/

[color=red]// Answer : D[/color]

 /**
 *
 * @author yaoyuan
 */

11	public static void main(String[] args){
12		try{
13			args = null;
14			aegs[0] = "test";
15			System.out.println(args[0]);
16		}catch(Exception ex){
17			System.out.println("Exception");
18		}catch(NullPointerException npe){
19			System.out.println("NullPointerException");
20		}
21	}

/**
*What is the result?
*
*
*A test
*B Exception
*C Compilation fails
*D NullPointerException
*/

[color=red]// Answer : C[/color]

 /**
 *
 * @author yaoyuan
 */
1	import java.util.*;
2	
3	public class LetterASort{
4		public static void main(String[] args){
5			ArrayList<String> strings = new ArrayList<String>();
6			strings.add("aAaA");
7			strings.add("AaAa");
8			strings.add("aAa");
9			strings.add("AAaa");
10			Collections.sort(strings);
11			for(String s : strings)	{System.out.print(s + " ");}
12		}
13	}

/**
*What is the result?
*
*
*A Compilation fails
*B aA aA aA a A A aa A aA
*C AA aa AaA aA aAa aA aA
*D A aA AA aa aA aA aAa
*E aAa AaA aA aA AA aa
*F An exception is thrown at runtime
*/
[color=red]
// Answer : C
[/color]

 /**
 *
 * @author yaoyuan
 */

1	import java.util.*;
2	public class WrappedString{
3		private String s;
4 		public WappedString(String s){this.s = s;}
5		public static void main(String[] args){
6			HashSet<Object> hs = new HashSet<Object>();
7			WappedString ws1 = new WappedString("aardvark");
8			WappedString ws2 = new WappedString("aardvark");
9			String s1 = new String("aardvark");
10			String s2 = new String("aardvark");
11			hs.add(ws1);hs.add(ws2);hs.add(s1);hs.add(s2);
12			System.out.println(hs.size());}}

/**
*What is the result?
*
*
*A 0
*B 1
*C 2
*D 3
*E 4
*F Compilation fails
*G An exception is thrown at runtime
*/

[color=red]// Answer : D[/color]