My Java Study Guide

Question 1

___________ is attached to the class of the composing class to denote the aggregation relationship with the composed object.

Accepted Answer

An empty diamond

Answer

A solid diamond

Answer

An empty oval

Answer

A solid oval

Question 2

Write an expression that creates a Double object for the number 5.3
[blank_start]_______________________________[blank_end]

Accepted Answer

new Double(5.3)

Question 3

Write an expression that returns a decimal integer from a binary string 1011
[blank_start]__________________________________[blank_end]

Accepted Answer

Integer.parseInt("1011", 2)

Question 4

Write an expression for the minimum int type value
[blank_start]______________________________[blank_end]

Accepted Answer

Integer.MIN_VALUE

Question 5

The type of the first argument in Integer.parseInt() can only be of the String type

Answer

true

Question 6

s1 and s2 reference the same String object
    String s1 = new String("foo");
    String s2 = s1;
    s1 += "bar";

Answer

true

Question 7

Which of the following are real StringBuilder methods?

Accepted Answer

insert

Accepted Answer

delete

Accepted Answer

reverse

Accepted Answer

setCharAt

Accepted Answer

append

Answer

clear

Answer

add

Question 8

A subclass is a subset of its superclass

Answer

true

Question 9

If a parameter is an object the formal and actual parameters will reference the same object

Answer

true

Question 10

The output of the following code is: [blank_start]_________[blank_end]
public class MainProgram {

public static void main(String[] args) {
		C shore = new C();	
	}
}

class A {
	public A() {
		System.out.print("A");
	}
}

class B extends A {
	public B() {
		System.out.print("B");
	}
}

class C extends B {
	
}

Accepted Answer

AB

Question 11

If a method defined in a subclass is private in its superclass, the two methods are completely unrelated.

Answer

true

Question 12

Overloading allows a programmer to have more than one method with the same name but with different signatures to distinguish them.

Answer

true

Question 13

Overriding allows a programmer to have more than one method with the same name but with different signatures to distinguish them.

Answer

true

Question 14

A method in a subclass can overload a method in the superclass

Answer

true

Question 15

You can pass a supertype variable to a subtype without explicit casting

Answer

true

Question 16

Which of these statements will cause an error?
public class Test {
  public static void main(String[] args) {
    m(new Pistol());
    m(new Gun());
    m(new Weapon());
    m(new Object());
  }

public static void m(Gun x) {
    System.out.println(x.toString());
  }
}

class Pistol extends Gun{
}

class Gun extends Weapon {
  @Override
  public String toString() {
    return "Gun";
  }
}

class Weapon extends Object {
  @Override
  public String toString() {
    return "Weapon";
  }
}

Accepted Answer

m(new Weapon());

Accepted Answer

m(new Object());

Answer

m(new Pistol());

Answer

m(new Gun());

Question 17

Casting an object reference variable affects the contents of the object.

Answer

true

Question 18

Primitive data type arrays are compatible with Object[]

Answer

true

Question 19

Suppose ArrayList x contains two strings [Beijing, Singapore]. Write a line of code to cause it to become [Beijing, Chicago, Singapore].
[blank_start]__________________________________[blank_end]

Accepted Answer

x.add(1,"Chicago");

Question 20

The arrayList's .remove() method will work if its only parameter is either an index or an item in the arrayList

Answer

true

Question 21

The array's .asList(array) method requires the array's contents be objects

Answer

true

Question 22

The methods in java.util.Collections work on Arrays

Answer

true

Question 23

Which of these classes cannot be extended?

Accepted Answer

final class foo{ }

Answer

class foo { }

Answer

class foo { private foo() { }}

Answer

class foo { protected foo() { }}

Answer

class foo { public foo() { }}

Question 24

This operation returns an exception:
long value = Long.MAX_VALUE + 1;

Answer

true

Question 25

An instance of _________ describes the errors caused by your program and external circumstances.

Accepted Answer

Exception

Answer

RuntimeException

Answer

Error

Answer

Throwable

Question 26

Write an expression that returns the size of the file for a File object f.
[blank_start]_____________________[blank_end]

Accepted Answer

f.length()

Question 27

Write an expression to test if a File object f represents a directory.
[blank_start]______________[blank_end]

Accepted Answer

f.isDirectory()

Question 28

Write an expression that tests if a File object f represents a file.
[blank_start]______________________[blank_end]

Accepted Answer

f.isFile()

Question 29

Enter an expression that returns the path separator character
[blank_start]_______________[blank_end]

Accepted Answer

File.pathSeparatorChar

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