2008 September « Nikos’ Java blog

Archive for September, 2008

SCJP Mock exam for new Java 6 features

13 September 2008

Questions 1-30 are about Console, 31-50 about NavigableSet and 51-80 about NavigableMap.

Console is a class. (1 correct answer)
1. true
2. false
Console belongs to the java.io package. (1 correct answer)
1. true
2. false
All the following methods are defined in Console.
    ⇒ readLine()
    ⇒ readPassword()
    ⇒ flush()
    ⇒ reader()
    ⇒ writer()
    ⇒ printf()
    ⇒ format()
1. True.
2. False.
Consider these methods.
    ⇒ readLine()
    ⇒ readPassword()
    ⇒ flush()
    ⇒ reader()
    ⇒ writer()
    ⇒ printf()
    ⇒ format()
How many of them are static? (1 correct answer)
1. Two.
2. Four.
3. All.
4. None.
Consider these methods.
    ⇒ readLine()
    ⇒ readPassword()
    ⇒ flush()
    ⇒ reader()
    ⇒ writer()
    ⇒ printf()
    ⇒ format()
How many of them declare a checked exception? (1 correct answer)
1. Two.
2. Four.
3. All.
4. None.
What’s the signature of the method readPassword()? (1 correct answer)
1. public char[] readPassword()
2. public byte[] readPassword()
3. public String readPassword()
What’s the signature of the method format()? (1 correct answer)
1. public void format(String, Object…)
2. public String format(String, Object…)
3. public Console format(String, Object…)
There are 2 overloaded methods of Console with the name readLine. (1 correct answer)
1. true
2. false
There are 2 overloaded methods of Console with the name getPassword. (1 correct answer)
1. true
2. false
There’s maximum one object of type Console available per JVM. (1 correct answer)
1. True.
2. False.

Will the following code compile successfully? (1 correct answer)

import java.io.Console;

public class MyConsole implements Console {

}

Yes.
No.

Will the following code compile successfully? (1 correct answer)
```
import java.io.Console;

public class MyConsole extends Console {

}
```
1. Yes.
2. No.

Will the following code compile successfully? (1 correct answer)

import java.io.Console;

public class Test {
    public static void main(String[] args) {
        Console console = new Console();
    }
}

Yes.
No.

Will the following code compile successfully? (1 correct answer)

import java.io.Console;

public class Test {
    public static void main(String[] args) {
        Console console = System.getConsole();
    }
}

Yes.
No.

Will the following code compile successfully? (1 correct answer)

import java.io.Console;

public class Test {
    public static void main(String[] args) {
        Console console = System.console();
    }
}

Yes.
No.

Will the following code compile successfully? (1 correct answer)

import java.io.Console;

public class Test {
    public static void main(String[] args) {
        Console console = System.console();
        console.println("Hello from your console!");
    }
}

Yes.
No.

Will the following code compile successfully? (1 correct answer)

import java.io.Console;

public class Test {
    public static void main(String[] args) {
        Console console = System.console();
        console.format("Hello from your console!");
    }
}

Yes.
No.

For this question only, consider that the underlying system does NOT provide a console. What happens when the following code is executed? (1 correct answer)
```
import java.io.Console;

public class Test {
    public static void main(String[] args) {
        Console console = System.console(); // 1
        console.format("Hello from your console!"); // 2
    }
}
```
1. A runtime exception is thrown at line 1
2. A runtime exception is thrown at line 2
3. No exception is thrown at runtime.

What happens when this code is compiled and executed? (1 correct answer)

import java.io.Console;

public class Test {
public static void main(String[] args) {
    Console console = System.console();
        console.readLine("Please enter your name: ");
        console.format(console.toString());
    }
}
}

Compilation fails.
An exception is thrown at runtime.
The console prints exactly what the user typed before pressing ENTER.
None of the above.

What happens when this code is compiled and executed? (1 correct answer)

import java.io.Console;

public class Test {
public static void main(String[] args) {
    Console console = System.console();
    if (console != null) {
        console.writer().close();
        console.printf("Hello!");
    }
}
}

Compilation fails.
An exception is thrown at runtime.
The console prints “Hello!”.
None of the above.

What happens when this code is compiled and executed? (1 correct answer)

import java.io.Console;

public class Test {
public static void main(String[] args) {
    Console console = System.console();
    if (console != null) {
    String name = console.
    readLine("Please enter your name: ");
    console.format("Hello %s!", name);
    }
}
}

Compilation fails.
An exception is thrown at runtime.
If the user enters “Nikos”, the console prints “Hello Nikos!”

What happens when this code is compiled and executed? (1 correct answer)

import java.io.Console;

public class Test {
public static void main(String[] args) {
    Console console = System.console();
    if (console != null) {
    String name = console.
    readLine("Please enter your name: ");
    console.format("Hello %z!", name);
    }
}
}

Compilation fails.
An exception is thrown at runtime.
If the user enters “Nikos”, the console prints “Hello Nikos!”

What happens when this code is compiled and executed? (1 correct answer)

import java.io.Console;

public class Test {
public static void main(String[] args) {
    Console console = System.console();
    if (console != null) {
    console.reader().close();
    String name = console.
    readLine("Please enter your name: ");
    console.format("Hello %s!", name);
    }
}
}

Compilation fails.
An exception is thrown at runtime.
If the user enters “Nikos”, the console prints “Hello Nikos!”

What happens when this code is compiled and executed? (1 correct answer)

import java.io.Console;
import java.io.IOException;

public class Test {
public static void main(String[] args) {
    Console console = System.console();
    try {
        console.reader().close();
    } catch (IOException e) {
    }
    String name = console.
    readLine("Please enter your name: ");
    console.format("Hello %s!", name);
}
}

Compilation fails.
An exception is thrown at runtime.
If the user enters “Nikos”, the console prints “Hello Nikos!”

What happens when this code is compiled and executed? (1 correct answer)

import java.io.Console;

public class Test {
public static void main(String[] args) {
    Console console = System.console();
    console.println("Hello!");
}
}

Compilation fails.
An exception is thrown at runtime.
The console prints “Hello!”.

What happens when this code is compiled and executed? (1 correct answer)

import java.io.Console;

public class Test {
public static void main(String[] args) {
    Console console = System.console();
    console.writer().println("Hello!");
}
}

Compilation fails.
An exception is thrown at runtime.
The console prints “Hello!”.

What happens when this code is compiled and executed? (1 correct answer)

import java.io.Console;

public class Test {
public static void main(String[] args) {
    Console console = System.console();
    console.writer().append("Hello ")
    .append("from ").append("console!");
    console.flush();
}
}

Compilation fails.
An exception is thrown at runtime.
The console prints “Hello from console!”.

What happens when this code is compiled and executed? (1 correct answer)

import java.io.Console;

public class Test {
public static void main(String[] args) {
    Console console = System.console();
    console.format("Hello!", null);
}
}

Compilation fails.
An exception is thrown at runtime.
The console prints “Hello!”.

What happens when this code is compiled and executed? (1 correct answer)

import java.io.Console;

public class Test {
public static void main(String[] args) {
    Console console = System.console();
    console.format(null);
}
}

Compilation fails.
An exception is thrown at runtime.
The console prints “null”.

What happens when this code is compiled and executed? (1 correct answer)

import java.io.Console;

public class Test {
public static void main(String[] args) {
    Console console = System.console();
    console.format("Hello ").printf("from ")
    .format("console!");
}
}

Compilation fails.
An exception is thrown at runtime.
The console prints “Hello from console!”.

NavigableSet is an interface. (1 correct answer)
1. true
2. false
NavigableSet extends SortedSet. (1 correct answer)
1. true
2. false
In Java 1.5 TreeSet implements SortedSet, whereas in Java 1.6 TreeSet implements NavigableSet. (1 correct answer)
1. true
2. false
All these methods belong to NavigableSet. (1 correct answer)
    lower()
    higher()
    floor()
    ceiling()
    pollFirst()
    pollLast()
1. true
2. false
How many of the following methods declare a checked exception? (1 correct answer)
    lower()
    higher()
    floor()
    ceiling()
    pollFirst()
    pollLast()
1. None.
2. Two.
3. Four.
4. All.
How many of the following methods may throw an exception at runtime? (1 correct answer)
    lower()
    higher()
    floor()
    ceiling()
    pollFirst()
    pollLast()
1. None.
2. Two.
3. Four.
4. All.
What’s the signature of the method lower()? (1 correct answer)
1. E lower(E)
2. boolean lower(E)
3. E lower(NavigableSet<E>)
What’s the signature of the method pollFirst()? (1 correct answer)
1. E pollFirst()
2. E pollFirst(E)
3. E pollFirst(NavigableSet<E>)
In the NavigableSet interface there are 2 overloaded methods with the name subSet. (1 correct answer)
1. true
2. false
In the NavigableSet interface there are 2 overloaded methods with the name headSet. (1 correct answer)
1. true
2. false