单项选择题

Which will declare a method that forces a subclass to implement it？（）

A. Public double methoda（）；
B. Static void methoda （double d1） {}
C. Public native double methoda（）；
D. Abstract public void methoda（）；
E. Protected void methoda （double d1）{}

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单项选择题

public class foo {
public static void main （String[]args） {
String s；
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.

单项选择题

int index = 1；
int [] foo = new int [3]；
int bar = foo [index]；
int baz = bar + index；
What is the result？（）

A. Baz has the value of 0
B. Baz has the value of 1
C. Baz has the value of 2
D. An exception is thrown.
E. The code will not compile.

单项选择题

public class test（
public static void main（string[]args）{
string foo = args [1]；
string foo = args [2]；
string foo = args [3]；
}
）
And command line invocation： Java Test red green blue
What is the result？（）

A. Baz has the value of “”
B. Baz has the value of null
C. Baz has the value of “red”
D. Baz has the value of “blue”
E. Bax has the value of “green”
F. The program throws an exception.