Java Exam2

Question 1

Which of the following is correct for a listener in context to event handling?

Accepted Answer

A listener is an object that is notified when an event occurs

Question 2

Which of the following exceptions is thrown in case when the file specified for within is not found?

Accepted Answer

FileNotFoundException

Question 3

In threading, which of the following is correct?

Accepted Answer

start() method creates new thread and calls code written in run() method

Question 4

Which of the following events is sent when a button is clicked?

Accepted Answer

ActionEvent

Question 5

American Express cards begin with a three followed by a four or seven and have 15 digits. Right a regular expression to verify an American Express credit card number.

Accepted Answer

^3[47][0-9]{13}\$

Question 6

Object of the matcher class is used to compile regular expressions.

Accepted Answer

False

Question 7

What statement will terminate another thread instance

Accepted Answer

Return

Question 8

The internet is a network of networks interconnected by switches

Accepted Answer

True

Question 9

It is generally not difficult to design a transport layer protocol to provide both high reliability and low delay for applications.

Accepted Answer

False

Question 10

Create a Regex to match "I want a bicycle.";

Accepted Answer

String string1 = "I want a bicycle."; System.out.println(string1.matches("I want a bicycle\.")); // true

Question 11

Write a regular expression that will match "I want a bike." and "I want a ball."

Accepted Answer

String string2 = "I want a bike.";
String string3 = "I want a ball.";
System.out.println(string2.matches("I want a (bike|ball)\\.")); // true
System.out.println(string3.matches("I want a (bike|ball)\\.")); // true

Question 12

Replace blanks w/ underscores in this string: Replace blanks w/ underscores

Accepted Answer

String string4 = "Replace all blanks with underscores."; String replaced = string4.replaceAll(" ", "_"); System.out.println(replaced); // "Replace_all_blanks_with_underscores."

Question 13

Write a regular expression that matches the following string using string.matches() String string5 = "aaabccccccdddefffg";

Accepted Answer

System.out.println(string5.matches("aaabccccccdddefffg")); // true

Question 14

Write a regular expression that will only match the string 5 above in its entirety.

Accepted Answer

System.out.println(string5.matches("^aaabccccccdddefffg$")); // true

Question 15

Write a sample program (code snippet) for thread join

Accepted Answer

class MyThread extends Thread {
public void run() {
System.out.println("Thread running...");
try {
Thread.sleep(2000);
} catch (InterruptedException e) {
System.out.println("Thread interrupted.");
}
}
}

public class ThreadJoinExample {
public static void main(String[] args) {
MyThread t1 = new MyThread();
t1.start();
try {
t1.join(); // Wait for t1 to finish
} catch (InterruptedException e) {
System.out.println("Main thread interrupted.");
}
System.out.println("Main thread continuing...");
}
}

Question 16

Create three threads: main, thread A and thread B. In the simulation you put thread aid to sleep for 10 seconds and after 10 seconds thread, a will wake up. After that thread B will join thread a. Make sure to handle exceptions such as one thread, interrupting another thread.

Accepted Answer

class A extends Thread {
public void run() {
try {
System.out.println("Thread A sleeping for 10 seconds...");
Thread.sleep(10000);
System.out.println("Thread A woke up!");
} catch (InterruptedException e) {
System.out.println("Thread A interrupted.");
}
}
}

class B extends Thread {
private Thread threadA;

public B(Thread threadA) {
this.threadA = threadA;
}

public void run() {
try {
threadA.join(); // Wait for Thread A to finish
System.out.println("Thread B started after Thread A.");
} catch (InterruptedException e) {
System.out.println("Thread B interrupted.");
}
}
}

public class ThreadExample {
public static void main(String[] args) {
A threadA = new A();
B threadB = new B(threadA);

threadA.start();
threadB.start();
}
}

Java Exam2

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