单项选择题
What will be written to the standard output when the following program is run？（）
public class Q03e4 {
public static void main（String args[]） {
String space = " "；
String composite = space + "hello" + space + space；
composite.concat（"world"）；
String trimmed = composite.trim（）；
System.out.println（trimmed.length（））；
}
}
A.5
B.6
C.7
D.12
E.13
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单项选择题
GiventhatfileisareferencetoaFileobjectthatrepresentsadirectory，whichcodefragmentswillsucceedinobtainingalistoftheentriesinthedirectory？（）
A.Vector filelist = （（Directory） file）.getList（）；
B.String[] filelist = file.directory（）；
C.Enumeration filelist = file.contents（）；
D.String[] filelist = file.list（）；
E.Vector filelist = （new Directory（file））.files（）； -
填空题
Given the following code, write a line of code that, when inserted at the indicated location, will make the overriding method in Extension invoke the overridden method in class Base on the current object. class Base { public void print() { System.out.println("base"); } } class Extention extends Base { public void print() { System.out.println("extension"); // insert line of implementation here } } public class Q294d { public static void main(String args[]) { Extention ext = new Extention(); ext.print(); } } Fill in a single line of implementation.（） -
单项选择题
Whichstatementsaretrue，giventhecodenewFileOutputStream（"data"，true）forcreatinganobjectofclassFileOutputStream？（）
A.FileOutputStream has no constructors matching the given arguments.
B.An IOExeception will be thrown if a file named "data" already exists.
C.An IOExeception will be thrown if a file named "data" does not already exist.
D.If a file named "data" exists， its contents will be reset and overwritten.
E.If a file named "data" exists， output will be appended to its current contents.
