String foo = “blue”；
Boolean[]bar = new Boolean [1]；
if （bar[0]） {
foo = “green”；
}
What is the result？ （）
A. Foo has the value of “”
B. Foo has the value of null.
C. Foo has the value of “blue”
D. Foo has the value of “green”
E. An exception is thrown.
F. The code will not compile.
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A. Char ch = “a”；
B. Char ch = ‘\’ ‘；
C. Char ch = ‘cafe’；
D. Char ch = “cafe”；
E. Char ch = ‘\ucafe’；
F. Char ch = ‘\u10100’；
G. Char ch = （char） true；
public class foo {
static String s；
public static void main （String[]args） {
system.out.printIn （“s=” + s）；
}
}
What is the result？（）
A. The code compiles and “s=” is printed.
B. The code compiles and “s=null” is printed.
C. The code does not compile because string s is not initialized.
D. The code does not compile because string s cannot be referenced.
E. The code compiles， but a NullPointerException is thrown when toString is called.
public interface Foo{
int k = 4；
}
Which three are equivalent to line 2？（）
A. Final int k = 4；
B. Public int k = 4；
C. Static int k = 4；
D. Private int k = 4；
E. Abstract int k = 4；
F. Volatile int k = 4；
int index = 1；
String [] test = new String[3]；
String foo = test[index]；
What is the result？（）
A. Foo has the value “”
B. Foo has the value null
C. An exception is thrown
D. The code will not compile
public class Test {
public static void main （String[]args） {
String foo = args[1]；
String bar = args[2]；
String baz = args[3]；
System.out.printIn（“baz = ” + baz）；
}
}
And the output：
Baz = 2
Which command line invocation will produce the output？（）
A. Java Test 2222
B. Java Test 1 2 3 4
C. Java Test 4 2 4 2
D. Java Test 4 3 2 1
1. package foo；
2.
3. import java.util.Vector；
4.
5. private class MyVector extends Vector {
6. int i = 1；
7. public MyVector（） {
8. i = 2；
9. }
10. }
11.
12. public class MyNewVector extends MyVector {
13. public MyNewVector （） {
14. i = 4；
15. }
16. public static void main （String args []） {
17. MyVector v = new MyNewVector（）；
18. }
19. }
The file MyNewVector.java is shown in the exhibit. What is the result？（）
A. Compilation will succeed.
B. Compilation will fail at line 5.
C. Compilation will fail at line 6.
D. Compilation will fail at line 14.
E. Compilation will fail at line 17.
class super {
public int getLength（） {return 4；}
}
public class Sub extends Super {
public long getLength（） {return 5；}
public static void main （String[]args） {
super sooper = new Super （）；
Sub sub = new Sub（）；
System.out.printIn（
sooper.getLength（）+ “，” + sub.getLength（） }；
}
What is the output？（）
A. 4， 4
B. 4， 5
C. 5， 4
D. 5， 5
E. The code will not compile.
A. The default constructor initializes method variables.
B. The compiler always creates a default constructor for every class.
C. The default constructor invokes the no-parameter constructor of the superclass.
D. The default constructor initializes the instance variables declared in the class.
E. When a class has only constructors with parameters， the compiler does not create a default constructor.
1. public class ArrayTest {
2. public static void main （String[]args） {
3. float f1[]， f2[]；
4. f1 = new float [10]；
5. f2 = f1；
6. System.out.printIn （“f2[0]=” + f2[0]）；
7. }
8. }
What is the result？（）
A. It prints f2[0] = 0.0
B. It prints f2[0] = NaN
C. An error at line 5 causes compile to fail.
D. An error at line 6 causes compile to fail.
E. An error at line 6 causes an exception at runtime.
ClassOne.java
1. package com.abc.pkg1；
2. public class ClassOne {
3. private char var = ‘a’；
4. char getVar（） {return var；}
5. }
ClassTest.java
1. package com.abc.pkg2；
2. import com.abc.pkg1.ClassOne；
3. public class ClassTest extends ClassOne {
4. public static void main（String[]args） {
5. char a = new ClassOne（）.getVar（）；
6. char b = new ClassTest（）.getVar（）；
7. }
8. }
What is the result？（）
A. Compilation will fail.
B. Compilation succeeds and no exceptions are thrown.
C. Compilation succeeds but an exception is thrown at line 5 in ClassTest.java.
D. Compilation succeeds but an exception is thrown at line 6 in ClassTest.java.
最新试题
Given： foo and bar are public references available to many other threads， foo refers to a Thread and bar is an Object. The thread foo is currently executing bar.wait（）. From another thread， what provides the most reliable way to ensure that foo will stop executing wait（）？（）
What is the result？（）
A programmer must create a generic class MinMax and the type parameter of MinMax must implement Comparable. Which implementation of MinMax will compile？（）
A programmer is developing a class Key， that will be used as a key in a standard java.util.HashMap. Which two methods should be overridden to assure that Key works correctly as a key？（）
What is the result？（）
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Given that Triangle implements Runnable， and：Which two statements， inserted independently at both lines 35 and 41， tend to allow both threads to temporarily pause and allow the other thread to execute？（）
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