Java: Test Java1

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Summary

Java căn bản (Variables and Operators, Decision – Making and Iterations)
Các phần liên quan đến class: tạo class, constructor, set/get, inheritance, override, overload
Package & Access Specifier
Interface
Nhập dữ liệu từ bàn phím (lớp Scanner)
Mảng
Chuỗi
Exception

Question Review

Introduction to java

1. Which is represent the behavior of an object

Class
Method đ úng
Object
Field

2. Which is an instance of a class

Class
Method
Object đ úng
Field

3. Which is represent the state of Object?.

Class
Object
Method
Field đúng

4. Which is describes an entity?

Class
Object đúng
Method
Field

Java APIs contain libraries of classes and other software components as interfaces

True đúng
False

5. JVM serves as the intermediary between a java program and a host computer

True đúng
False

6. The java JDK does not include APIs

True
False đung

7. JVM is not available on different operating systems

True
False đúng

8. Which is the feature of java provides security control

Distributed
Object – Oriented
Secure đúng
Multithreading

9. Which is the feature of java provides support for performing many tasks simultaneously

Distributed
Platform – independent
Object – Oriented
Multithreading

10. Which is the feature of java can run on any machine

Distributed
Platform – independent đ úng
Object – Oriented
Multithreading

11. The javac tool invokes the java compiler

True đ úng
False
The java tool invokes the java interpreter

True
False đ úng

12. The .class files contain bytecodes.

True đ úng
False
The java interpreter compiles code

True đ úng
False

13. A multi-line comment starts with forward slash and a hash (/#)

True
False đ úng
A java doc comment ends with double asterisk and forward slash (**/)

True
False đ úng

14. Comment appears within delimiters

True đ úng
False

Variables and Operators

1. Variable need not to initialized when declared

True đ úng
False

2. Variable names $bank_account and _1account are valid.

True đ úng
False

3. Only one variable can be declared in a statement at a time

True
False đung

4. Variable can be declared to store any type of value

True đ úng
False

5. You are trying to use the form at specifiers to display the output:

“100*55.0=5500.000”, “100*55.0=5500.000000”,”100*55.0=5.50e+3” and “100*55.0=0”

Which of the following codes will help you achieve this

a. double result = 100*55.0;

int =0;

System.out.printf(“100 * 55.0 = %1.3f %n”, result);

System.out.printf(“100 * 55.0 = %5f %n”, result);

System.out.printf(“100 * 55.0 = %1.5f %n”, result);

System.out.printf(“100 * 55.0 = %d %n”, q);

b. double result = 100*55.0;

int =0;

System.out.printf(“100 * 55.0 = %1.3f %n”, result);

System.out.printf(“100 * 55.0 = %5f %n”, result);

System.out.printf(“100 * 55.0 = %1.2e %n”, result); đ úng

System.out.printf(“100 * 55.0 = %d %n”, q);

c. double result = 100*55.0;

int =0;

System.out.printf(“100 * 55.0 = %09.3f %n”, result);

System.out.printf(“100 * 55.0 = %5f %n”, result);

System.out.printf(“100 * 55.0 = %f %n”, result);

System.out.printf(“100 * 55.0 = %d %n”, q);

d. double result = 100*55.0;

int =0;

System.out.printf(“100 * 55.0 = %3f %n”, result);

System.out.printf(“100 * 55.0 = %5f %n”, result);

System.out.printf(“100 * 55.0 = %1.2e %n”, result);

System.out.printf(“100 * 55.0 = %d %n”, q);

6. The nextDouble() method of Scanner class return the next token as a byte value

True
False đ úng

7. The nextByte() method of Scanner class return the next token as a byte value

True đ úng
False

8. You are using various operators to solve an expression. Which of the following statements will display the output as “true”

a. int a=5, b=4, c=3, d=2, e=1;

System.out.println((a+b/5.0-c*d+1*e>(a*b)&&(b<d));

b. int a=5, b=4, c=3, d=2, e=1;

System.out.println((a+b/5.0+c*d+1*e>(a/b)&&(b>d)); đ úng

c. int a=5, b=4, c=3, d=2, e=1;

System.out.println((a+b+5.0-c*d+1*e<(a*b)&&(b>d));

d. int a=5, b=4, c=3, d=2, e=1;

System.out.println((a+b/5.0-c*d*1*e>(a*b)&&(b<d));

9. you want the output to be displayed as “Value of floatTest after conversion: 1.0”, “Value of dblTest after conversion: 1.0” and “Value of sum after conversion: 2”. Can you arrange the steps in sequences to achieve the same

a. System.out.println(“dblTest=”+dblTest);

int sum = (int)(floatTest+dblTest);

b. System.out.println(“Sum = “+sum);

c. boolean boolTest = true;

float floatTest = 3.14f;

d. System.out.println(“floatTest = “+floatTest);

dblTest = (double)(boolTest ? 1:0);

e. double dblTest = 0.0000000053;

floatTest = (float)(boolTest? 1:0);

Decision-making and Iterations

1. You are trying to use the if statement to display the value “100 Not Equal”. Which of the follow code will help you achieve this.

a. int value = 100;

boolean bool = true;

if((bool==true)&&((value+=100)==200)){

System.out.printf(“Equal “+value);

}else{

System.out.println(value+” Not Equal”);

}

b. int value = 100;

boolean bool = false;

if((bool==true)&&((value==100)==200)){

System.out.printf(“Equal “+value);

}else{

System.out.println(value+” Not Equal”);

}

c. int value = 100;

boolean bool = true;

if((bool==false)&&((value+=100)==200)){

System.out.printf(“Equal “+value);

}else{

System.out.println(value+” Not Equal”);

}

d. int value = 100;

boolean bool = true;

if((bool==true)&&((value+=100)==200)){

System.out.printf(“Equal “+value);

}else{

System.out.println(value+” Not Equal”);

}

2. You are using switch – case statement to display the output “value is ten” and “value is twenty”. Which of the following code will help you achieve this

a. int value = 10;

switch(value){

default:

System.out.println(“Invalid value”);

break;

case 10:

System.out.println(“value is ten”):

break;

case 20:

System.out.println(“value is twenty”);

break;

}

b. int value = 10;

switch(value){

default:

System.out.println(“Invalid value”);

break;

case 10:

System.out.println(“value is ten”):

break;

case 20:

System.out.println(“value is twenty”);

}

c. int value = 10;

switch(value){

default:

System.out.println(“Invalid value”);

break;

case 10:

System.out.println(“value is ten”):

case 20:

System.out.println(“value is twenty”);

break;

}

d. int value = 10;

switch(value){

default:

System.out.println(“Invalid value”);

break;

case 10:

System.out.println(“value is ten”):

case 20:

System.out.println(“value is twenty”);

}

3. You want the output to be display as “95 91 87 83”. Can you arrange the steps in the sequence to achieve the same

System.out .println(i);
i++;}
int i=100
i-=5;
while (i>=85){

4. do – while test the condition after the first iteration of the loop

True đ úng
False

5. In do – while, if the condition is true, the control passes back to the top of the loop

True đung
False

6. In do-while if the condition is true, the loop terminates

True
False đ úng

7. do – while statements is executed at least one

True đ úng
False

8. do – while tests the condition at the beginning of the loop

True
False đ úng

9. You want to display the output as “15105”. Can you indentify the correct code

a. for (int i=15; i>=0; i-=5)

System.out.print(i);

System.out.println(“”);

b. for (int i=11; i<=15; i+=5)

System.out.print(i);

System.out.println(“”);

c. for (int i=15; i>0; i-=5) đ úng

System.out.print(i);

System.out.println(“”);

d. for (int i=15; i>=0; i-=6)

System.out.print(i);

System.out.println(“”);

10. Executed at least once before the condition is checked at the end of the loop

while
do – while đ úng
for

11. Used when the user is sure about the number of the iterations required

while
do – while
for đug

12. Variable used in the expression initialized before the loop starts

while
do – while
for đ úng

13. This control structure is known as post-test loop

while
do – while
for

14. You are using a code snippet to print the value of sum as “6”. Which of the following code snippet will help you to achieve this

a. int sum =0;

int number = 1;

do{

number++;

sum +=number;

if (sum>4) break;

} while ( number<5);

System.out.println(sum);

b. int sum =0;

int number = 0;

do{

number++;

sum +=number;

if (sum>6) break;

} while ( number<5);

System.out.println(sum);

c. int sum =0;

int number = 0;

do{

number++;

sum +=number;

if (sum>4) break;

} while ( number<5);

System.out.println(sum);

d. int sum =0;

int number = 0;

do{

number++;

sum +=number;

if (sum>4) break;

} while ( number==5);

System.out.println(sum);

Introducing classes

1. Class names cannot be a keyword in java

True dung
False

2. Class names can be in mixed case

True đung
False

3. Declaration of the class need not be preceded with the keyword class

True
False đ úng

4. Class names can be begin with a digit

True
False đ úng

5. Class names can be begin with a dollar symbol or an underscore character

True đ úng
False

6. Constructor is executed when a class is created

True đ úng
False

7. Constructors does not have parameters but have return types

True
False đ úng

8. The new keyword creates an object of the class

True đ úng
False

9. Constructors have the same name as that of the class

True đ úng
False

10. A default no – argument constructor has to be defined for every class

True đ úng
False

11. You want to declare class Student containing an instance variable rollNo. Further you want to create two instances of this class namely objJohn and objMartin, assign value to their respective instance variable and display them. Can you arrange the steps in sequence to achieve the same

a. objJohn.rollNo = 1151;

Student objMartin = new Student();

b. public static void main(String[] arg){

Student objJohn = new Student();

c. System.out.println( objMartin.rollNo);

}}

d. objMartin.rollNo=1152;

System.out.println(objJohn.rollNo);

e. class Student{

int rollNo;

12. You are trying to define an instance method, display for a class named complex. The class contains two instance variables namely real and imaginary. The method, display should accept an object of type complex and display the values of its instance variables. Which of following code will help you achieve this

a. Void display(Complex obj){

System.out.println(real);

System.out.println(imaginary);

}

b. Void display(Complex obj){

System.out.println(obj.real);

System.out.println(obj.imaginary);

}

c. Complex display(Complex obj){

System.out.println(obj.real);

System.out.println(obj.imaginary);

}

d. Void display(){

Complex obj = new Complex();

System.out.println(obj.real);

System.out.println(obj.imaginary);

}

13. Class block initialize is used to initialize complex classes and the initialization code is preceded with static keyword.

True
False

14. Class field initializer is used initialize classes variables

True
False

15. Class field initialization code is preceded with a static keyword.

True
False

16. Object block initializer consists of open and close brace and the initialization code

True
False

Arrays

1. You are trying to create an array of ten elements and store the first ten even numbers within it and display the same. Which of the following code will help you achieve this

a. int[] evenNumbers = new int[10];

int number = 2;

for(int count = 0; count<10; count++){

number +=2;

evenNumbers[count]=number;

}

for (count =0; count<10;count++){

System.out.println(evenNumbers[count]);

}

b. int[] evenNumbers = new int[10];

for(int count = 0, number =1; count<10; count++,number++){

number ++;

evenNumbers[count]=number;

}

for (count =0; count<10;count++){

System.out.println(evenNumbers[count]);

}

c. int[] evenNumbers = new int[10];

for(int count = 0, number =2; count<10; count++,number++){

evenNumbers[count]=number;

number = number +2;

}

for (count =0; count<10;count++){

System.out.println(evenNumbers[count]);

}

d. int[] evenNumbers = new int[10];

int number = 0

for(int count = 0, number =1; count<10; count++,number+=2){

evenNumbers[count]=number;

}

for (count =0; count<10;count++){

System.out.println(evenNumbers[count]);

}

2. You are trying to compute the average of temperatures recorded for 50 cities in 365 days using two – dimentional array temps. Average temperature is obtained by adding each day’s temperature and dividing it by 365. Which of following code will help you achieve this.

a. for (int city =0; city<50; city++){

int total;

for(int day =0;day<365; day++{

total = total+temps[city][day];

}

double average = total/365.0;

System.out.println(“Temperature for city “+city +” is “+average);

}

b. for (int city =0; city<50; city++){

int total = 0;

double average = 0;

for(int day =0;day<365; day++{

total = total+temps[city][day];

average = total/day;

}

System.out.println(“Temperature for city “+city +” is “+average);

}

c. for (int city =0; city<50; city++){

int total = 0;

for(int day =0;day<365; day++{

total = total+temps[city][day];

}

double average = total/365.0;

System.out.println(“Temperature for city “+city +” is “+average);

}

d. for (int city =0; city<50; city++){

int total = 0;

double average = 0;

for(int day =0;day<365; day++{

total = total+temps[city][day];

average = total+day;

}

System.out.println(“Temperature for city “+city +” is “+average);

}

3. Use to get the character value at the specified index

lastIndexOf
indexOf
charAt đ úng

4. Use to compare two object and returns an integer

substring
compareTo đ úng

5. Can you indentify the correct parameter specifications for the main method

String[] args đ úng
String args
String args[] đ úng
String arguments
String arguments()
String arguments{}

6. Append values to the end of the StringBuilder object

append
insert

Package and Access specifiers

1. A package can comprise of classes, interface and packages

True
False

2. A class when defined without any package, result in a compile time error

True
False

3. The fully qualified name of java class included package name

True
False

4. A package does not provide access protection and namespace management

True
False

5. While creating packages, the package statement must be the first statement in the source file

True
False

6. Allows member of a class to be accessible in all class belonging to that package in which the class is defined

default
public
private
protect

7. Allows member of a class to be accessible only within the class and within the methods of the class

public
private
protect

8. Allows member of a class to be accessible from any class.

Public
Private
Protect

9. Allows member of a class to be accessible from another class in another package

Public
Private
Protect

10. Which of the following code will generate compile-time error

a. Class First{

int x = 7;

}

class Second{

public static void main(String[] args){

First fst = new First()

System.out.println(fst.x);

}

b. class First{

int x = 7;

}

class Second{

public static void main(String[] args){

First fst = new First()

System.out.println(fst.x);

}

c. class First{

public int x = 7;

}

class Second{

public static void main(String[] args){

First fst = new First()

System.out.println(fst.x);

}

d. class First{

protect int x = 7;

}

class Second{

public static void main(String[] args){

First fst = new First()

System.out.println(fst.x);

}

11. final fields cannot be volatile

True
False

12. A transient modifier is used to declare fields that are not saved or restored as part of the state of the object

True
False

13. Native method are not coded in java

True
False

14. Volatile is applied only to constructors, methods, classes and interfaces

True
False

15. Native modifier can be apply to constructors, fields, classes and interfaces

True
False

Inheritance and interface

1. If a class does not have any super class. Then it is implicitly derived from Object class Which is parent of all java class

True
False

2. The process, whereby characteristics and behavior are transmitted from parent to child entity, is called inheritance

True
False

3. Inheritance saves time and encourages code reuse and customization

True
False

4. A class can be derived from several classes

True
False

5. Super keyword allows the method of super class to be invoked from subclass method

True
False

6. super() invoked default constructor of super class

True
False

7. super() can be place anywhere in the constructor of the subclass

True
False

8. The overriding method must have the same signature as the overridden method

True
False

9. The access specifier of the overriding method and the overridden method have to public

True
False

10. Indentify the code that overloads method Draw();

a. public class Shape{

public void Draw(){