J2EE测试31－40题

31Given the following code fragment:
1) String str = null;
2) if ((str != null) && (str.length() > 10)) {
3) System.out.println("more than 10");
4) }
5) else if ((str != null) & (str.length() < 5)) {
6) System.out.println("less than 5");
7) }
8) else { System.out.println("end"); }
Which line will cause error?

A. line 1
B. line 2
C. line 5
D. line 8

32Which statements about Java code security are true?

A. The bytecode verifier loads all classes needed for the execution of a program.
B. Executing code is performed by the runtime interpreter.
C. At runtime the bytecodes are loaded, checked and run in an interpreter.
D. The class loader adds security by separating the namespaces for the classes of the local file system from those imported form network sources.

33Given the following code:
public class Person{
static int arr[] = new int[10];
public static void main(String a[]) {
System.out.println(arr[1];)
}
}
Which statement is correct?

A. When compilation some error will occur.
B. It is correct when compilation but will cause error when running.
C. The output is zero.
D. The output is null.

34Given the following code:
public class Person{
int arr[] = new int[10];
public static void main(String a[]) {
System.out.println(arr[1];)
}
}
Which statement is correct?

A. When compilation some error will occur.
B. It is correct when compilation but will cause error when running.
C. The output is zero.
D. The output is null.

35public class Parent {
public int addValue( int a, int b) {
int s;
s = a+b;
return s;
}
}
class Child extends Parent {

}
Which methods can be added into class Child?

A. int addValue( int a, int b ){// do something...}
B. public void addValue (){// do something...}
C. public int addValue( int a ){// do something...}
D. public int addValue( int a, int b )throws MyException {//do something...}

36A member variable defined in a class can be accessed only by the classes in the same package. Which modifier should be used to obtain the access control?

A. private
B. no modifier
C. public
D. protected

37A public member vairable called MAX_LENGTH which is int type, the value of the variable remains constant value 100. Use a short statement to define the variable.

A. public int MAX_LENGTH=100;
B. final int MAX_LENGTH=100;
C. final public int MAX_LENGTH=100;
D. public final int MAX_LENGTH=100.

38Which expressions are correct to declare an array of 10 String objects?

A. char str[];
B. char str[][];
C. String str[];
D. String str[10];

39Which fragments are correct in Java source file?

A. package testpackage;
public class Test{//do something...}
B. import java.io.*;
package testpackage;
public class Test{// do something...}
C. import java.io.*;
class Person{// do something...}
public class Test{// do something...}
D. import java.io.*;
import java.awt.*;
public class Test{// do something...}

40String t = "hello";
char c[] = {'h','e','l','l','o'} ;
Which return true?

A. s.equals(t);
B. t.equals(c);
C. s==t;
D. t.equals(new String("hello"));
E. t==c.

(c),(bcd),(c),(a),(bc),(b),(d),(c),(acd),(ad)