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Self Test (Strings, I/O, Formatting, and Parsing)

1. Given:

import java.util.regex.*;
class Regex2 {
public static void main(String[] args) {
Pattern p = Pattern.compile(args[0]);
Matcher m = p.matcher(args[1]);
boolean b = false;
while(b = m.find()) {
System.out.print(m.start() + m.group());
}
}
}

And the command line:

java Regex2 "\d*" ab34ef

What is the result?

A. 234
B. 334
C. 2334
D. 0123456
E. 01234456
F. 12334567
G. Compilation fails.

2. Given:

import java.io.*;
class Player {
Player() { System.out.print("p"); }
}
class CardPlayer extends Player implements Serializable {
CardPlayer() { System.out.print("c"); }
public static void main(String[] args) {
CardPlayer c1 = new CardPlayer();
try {
FileOutputStream fos = new FileOutputStream("play.txt");
ObjectOutputStream os = new ObjectOutputStream(fos);
os.writeObject(c1);
os.close();
FileInputStream fis = new FileInputStream("play.txt");
ObjectInputStream is = new ObjectInputStream(fis);
CardPlayer c2 = (CardPlayer) is.readObject();
is.close();
} catch (Exception x ) { }
}
}

What is the result?

A. pc
B. pcc
C. pcp
D. pcpc
E. Compilation fails.
F. An exception is thrown at runtime.

3. Given that bw is a reference to a valid BufferedWriter And the snippet:

15. BufferedWriter b1 = new BufferedWriter(new File("f"));
16. BufferedWriter b2 = new BufferedWriter(new FileWriter("f1"));
17. BufferedWriter b3 = new BufferedWriter(new PrintWriter("f2"));
18. BufferedWriter b4 = new BufferedWriter(new BufferedWriter(bw));

What is the result?

A. Compilation succeeds.
B. Compilation fails due only to an error on line 15.
C. Compilation fails due only to an error on line 16.
D. Compilation fails due only to an error on line 17.
E. Compilation fails due only to an error on line 18.
F. Compilation fails due to errors on multiple lines.

4. Given:

class TKO {
public static void main(String[] args) {
String s = "-";
Integer x = 343;
long L343 = 343L;
if(x.equals(L343)) s += ".e1 ";
if(x.equals(343)) s += ".e2 ";
Short s1 = (short)((new Short((short)343)) / (new Short((short)49)));
if(s1 == 7) s += "=s ";
if(s1 < new Integer(7+1)) s += "fly ";
System.out.println(s);
}
}

Which of the following will be included in the output String s? (Choose all that apply.)

A. .e1
B. .e2
C. =s
D. fly
E. None of the above.
F. Compilation fails.
G. An exception is thrown at runtime.

5. Given:

1. import java.text.*;
2. class DateOne {
3. public static void main(String[] args) {
4. Date d = new Date(1123631685981L);
5. DateFormat df = new DateFormat();
6. System.out.println(df.format(d));
7. }
8. }

And given that 1123631685981L is the number of milliseconds between Jan. 1, 1970, and sometime on Aug. 9, 2005, what is the result? (Note: the time of day in option A may vary.)

A. 8/9/05 5:54 PM
B. 1123631685981L
C. An exception is thrown at runtime.
D. Compilation fails due to a single error in the code.
E. Compilation fails due to multiple errors in the code.

6. Given:

import java.io.*;
class Keyboard { }
public class Computer implements Serializable {
private Keyboard k = new Keyboard();
public static void main(String[] args) {
Computer c = new Computer();
c.storeIt(c);
}
void storeIt(Computer c) {
try {
ObjectOutputStream os = new ObjectOutputStream(
new FileOutputStream("myFile"));
os.writeObject(c);
os.close();
System.out.println("done");
} catch (Exception x) {System.out.println("exc"); }
}
}

What is the result? (Choose all that apply.)

A. exc
B. done
C. Compilation fails.
D. Exactly one object is serialized.
E. Exactly two objects are serialized.

7. Using the fewest fragments possible (and filling the fewest slots possible), complete the code below so that the class builds a directory named "dir3" and creates a file named "file3" inside "dir3". Note you can use each fragment either zero or one times. Code:

import java.io.______________
class Maker {
public static void main(String[] args) {
___________ ___________ ___________
___________ ___________ ___________
___________ ___________ ___________
___________ ___________ ___________
___________ ___________ ___________
___________ ___________ ___________
___________ ___________ ___________
}
}
Fragments:

File;     FileDescriptor;     FileWriter;     Directory;
try {     .createNewDir();     File dir         File
{ }     (Exception x)         ("dir3");         file
file     .createNewFile();     = new File         = new File
dir     (dir, "file3");     (dir, file);     .createFile();
} catch ("dir3", "file3");     .mkdir();         File file

8. Which are true? (Choose all that apply.)

A. The DateFormat.getDate() is used to convert a String to a Date instance.
B. Both DateFormat and NumberFormat objects can be constructed to be Locale specific.
C. Both Currency and NumberFormat objects must be constructed using static methods.
D. If a NumberFormat instance's Locale is to be different than the current Locale, it must be specified at creation time.
E. A single instance of NumberFormat can be used to create Number objects from Strings and to create formatted numbers from numbers.

9. Which will compile and run without exception? (Choose all that apply.)

A. System.out.format("%b", 123);
B. System.out.format("%c", "x");
C. System.out.printf("%d", 123);
D. System.out.printf("%f", 123);
E. System.out.printf("%d", 123.45);
F. System.out.printf("%f", 123.45);
G. System.out.format("%s", new Long("123"));

10. Which about the three java.lang classes String, StringBuilder, and StringBuffer are true? (Choose all that apply.)

A. All three classes have a length() method.
B. Objects of type StringBuffer are thread-safe.
C. All three classes have overloaded append() methods.
D. The "+" is an overloaded operator for all three classes.
E. According to the API, StringBuffer will be faster than StringBuilder under most implementations.
F. The value of an instance of any of these three types can be modified through various methods in the API.

11. Given that 1119280000000L is roughly the number of milliseconds from Jan. 1, 1970, to June 20, 2005, and that you want to print that date in German, using the LONG style such that "June" will be displayed as "Juni", complete the code using the fragments below. Note: you can use each fragment either zero or one times, and you might not need to fill all of the slots. Code:

import java.___________
import java.___________
class DateTwo {
public static void main(String[] args) {
Date d = new Date(1119280000000L);
DateFormat df = ___________________________
________________ , _________________ );
System.out.println(________________
}
}

Fragments:

io.*;         new DateFormat(                 Locale.LONG
nio.*;         DateFormat.getInstance(         Locale.GERMANY
util.*;     DateFormat.getDateInstance(     DateFormat.LONG
text.*;     util.regex;                     DateFormat.GERMANY
date.*;     df.format(d));                     d.format(df));

12. Given:

import java.io.*;
class Directories {
static String [] dirs = {"dir1", "dir2"};
public static void main(String [] args) {
for (String d : dirs) {
// insert code 1 here
File file = new File(path, args[0]);
// insert code 2 here
}
}
}
and that the invocation

java Directories file2.txt

is issued from a directory that has two subdirectories, "dir1" and "dir1", and that "dir1" has a file "file1.txt" and "dir2" has a file "file2.txt", and the output is "false true"; which set(s) of code fragments must be inserted? (Choose all that apply.)

A. String path = d;
System.out.print(file.exists() + " ");
B. String path = d;
System.out.print(file.isFile() + " ");
C. String path = File.separator + d;
System.out.print(file.exists() + " ");
D. String path = File.separator + d;
System.out.print(file.isFile() + " ");

13. Given:

class Polish {
public static void main(String[] args) {
int x = 4;
StringBuffer sb = new StringBuffer("..fedcba");
sb.delete(3,6);
sb.insert(3, "az");
if(sb.length() > 6) x = sb.indexOf("b");
sb.delete((x-3), (x-2));
System.out.println(sb);
} }

What is the result?

A. .faza
B. .fzba
C. ..azba
D. .fazba
E. ..fezba
F. Compilation fails.
G. An exception is thrown at runtime.

14. Given:

1. import java.util.*;
2. class Brain {
3. public static void main(String[] args) {
4. // insert code block here
5. }
6. }

Which, inserted independently at line 4, compile and produce the output "123 82"? (Choose all that apply.)

A. Scanner sc = new Scanner("123 A 3b c,45, x5x,76 82 L");
while(sc.hasNextInt()) System.out.print(sc.nextInt() + " ");
B. Scanner sc = new Scanner("123 A 3b c,45, x5x,76 82 L").
useDelimiter(" ");
while(sc.hasNextInt()) System.out.print(sc.nextInt() + " ");
C. Scanner sc = new Scanner("123 A 3b c,45, x5x,76 82 L");
while(sc.hasNext()) {
if(sc.hasNextInt()) System.out.print(sc.nextInt() + " ");
else sc.next(); }
D. Scanner sc = new Scanner("123 A 3b c,45, x5x,76 82 L").
useDelimiter(" ");
while(sc.hasNext()) {
if(sc.hasNextInt()) System.out.print(sc.nextInt() + " ");
else sc.next(); }
E. Scanner sc = new Scanner("123 A 3b c,45, x5x,76 82 L");
do {
if(sc.hasNextInt()) System.out.print(sc.nextInt() + " ");
} while ( sc.hasNext() );
F. Scanner sc = new Scanner("123 A 3b c,45, x5x,76 82 L").
useDelimiter(" ");
do {
if(sc.hasNextInt()) System.out.print(sc.nextInt() + " ");
} while ( sc.hasNext() );

15. Given:

import java.io.*;
public class TestSer {
public static void main(String[] args) {
SpecialSerial s = new SpecialSerial();
try {
ObjectOutputStream os = new ObjectOutputStream(
new FileOutputStream("myFile"));
os.writeObject(s); os.close();
System.out.print(++s.z + " ");
ObjectInputStream is = new ObjectInputStream(
new FileInputStream("myFile"));
SpecialSerial s2 = (SpecialSerial)is.readObject();
is.close();
System.out.println(s2.y + " " + s2.z);
} catch (Exception x) {System.out.println("exc"); }
}
}
class SpecialSerial implements Serializable {
transient int y = 7;
static int z = 9;
}

Which are true? (Choose all that apply.)

A. Compilation fails.
B. The output is 10 0 9
C. The output is 10 0 10
D. The output is 10 7 9
E. The output is 10 7 10
F. In order to alter the standard deserialization process you would override the readObject() method in SpecialSerial.
G. In order to alter the standard deserialization process you would override the defaultReadObject() method in SpecialSerial.

Self Test Strings , I/O , Formatting , and Parsing ,