public class NamedCounter {
private final String name;
private int count;
public NamedCounter(String name) { this.name = name; }
public String getName() { return name; }
public void increment() { coount++; }
public int getCount() { return count; }
public void reset() { count = 0; } }
Which three changes should be made to adapt this class to be used safely by multiple threads? ()
A. declare reset() using the synchronized keyword
B. declare getName() using the synchronized keyword
C. declare getCount() using the synchronized keyword
D. declare the constructor using the synchronized keyword
E. declare increment() using the synchronized keyword
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public class TwoThreads {
private static Object resource = new Object();
private static void delay(long n) {
try { Thread.sleep(n); }
catch (Exception e) { System.out.print(”Error “); }
}
public static void main(String[] args) {
System.out.print(”StartMain “);
new Thread1().start();
delay(1000);
Thread t2 = new Thread2();
t2.start();
delay(1000);
t2.interrupt
delay(1000);
System.out.print(”EndMain “);
}
static class Thread 1 extends Thread {
public void run() {
synchronized (resource) {
System.out.print(”Startl “);
delay(6000);
System.out.print(”End1 “);
}
}
}
static class Thread2 extends Thread {
public void run() {
synchronized (resource) {
System.out.print(”Start2 “);
delay(2000);
System.out.print(”End2 “);
}
}
}
}
Assume that sleep(n) executes in exactly m milliseconds, and all other code executes in an insignificant amount of time. What is the output if the main() method is run?()
A. Compilation fails.
B. Deadlock occurs.
C. StartMain Start1 Error EndMain End1
D. StartMain Start1 EndMain End1 Start2 End2
E. StartMain Start1 Error Start2 EndMain End2 End1
F.StartMain Start1 EndMain End1 Start2 Error End2
public class TestOne implements Runnable {
public static void main (String[] args) throws Exception {
Thread t = new Thread(new TestOne());
t.start();
System.out.print(”Started”);
t.join();
System.out.print(”Complete”);
}
public void run() {
for (int i= 0; i< 4; i++) {
System.out.print(i);
}
}
}
What can be a result?()
A. Compilation fails.
B. An exception is thrown at runtime.
C. The code executes and prints “StartedComplete”.
D. The code executes and prints “StartedComplete0123”.
E. The code executes and prints “Started0l23Complete”.
public class TestOne {
public static void main (String[] args) throws Exception {
Thread.sleep(3000);
System.out.println(”sleep”);
}
}
What is the result?()
A. Compilation fails.
B. An exception is thrown at runtime.
C. The code executes normally and prints “sleep”.
D. The code executes normally, but nothing is printed.
public class Threads2 implements Runnable {
public void nun() {
System.out.println(”run.”);
throw new RuntimeException(”Problem”);
}
public static void main(String[] args) {
Thread t = new Thread(new Threads2());
t.start();
System.out.println(”End of method.”);
}
}
Which two can be results?()
A. java.lang.RuntimeException: Problem
B. run. java.lang.RuntimeException: Problem
C. End of method. java.lang.RuntimeException: Problem
D. End of method. run. java.lang.RuntimeException: Problem
E. run. java.lang.RuntimeException: Problem End of method.
public class Starter extends Thread {
private int x= 2;
public static void main(String[] args) throws Exception {
new Starter().makeItSo();
}
public Starter() {
x=5;
start();
}
public void makeItSo() throws Exception {
join();
x=x- 1;
System.out.println(x);
}
public void run() { x *= 2; }
}
What is the output if the main() method is rum?()
A. 4
B. 5
C. 8
D. 9
E. Compilation fails.
F. An exception is thrown at runtime.
G. It is impossible to determine for certain.
Runnable r = new Runnable() {
public void run() {
System.out.print(”Cat”);
}
};
Threadt=new Thread(r) {
public void run() {
System.out.print(”Dog”);
}
};
t.start();
What is the result?()
A. Cat
B. Dog
C. Compilation fails.
D. The code runs with no output.
E. An exception is thrown at runtime.
public class Threads5 {
public static void main (String[] args) {
new Thread(new Runnable() {
public void run() {
System.out.print(”bar”);
}
}).start();
}
}
What is the result?()
A. Compilation fails.
B. An exception is thrown at runtime.
C. The code executes normally and prints “bar”.
D. The code executes normally, but nothing prints.
public class Threads4 {
public static void main (String[] args) {
new Threads4().go();
}
public void go() {
Runnable r = new Runnable() {
public void run() {
System.out.print(”foo”);
}
};
Thread t = new Thread(r);
t.start();
t.start();
}
}
What is the result?()
A. Compilation fails.
B. An exception is thrown at runtime.
C. The code executes normally and prints „foo”.
D. The code executes normally, but nothing is printed.
public class Threads3 implements Runnable {
public void run() {
System.out.print(”running”);
}
public static void main(String[] args) {
Thread t = new Thread(new Threads3());
t.run();
t.run();
t.start();
}
}
What is the result?()
A. Compilation fails.
B. An exception is thrown at runtime.
C. The code executes and prints “running”.
D. The code executes and prints “runningrunning”.
E. The code executes and prints “runningrunningrunning”.
A. new Thread() { public void run() { doStuff(); } }
B. new Thread() { public void start() { doStuff(); } }
C. new Thread() { public void start() { doStuff(); } } .run();
D. new Thread() { public void run() { doStuff(); } } .start();
E. new Thread(new Runnable() { public void run() { doStuff(); } } ).run();
F. new Thread(new Runnable() { public void run() { doStuff(); } }).start();
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