Object-Oriented Programming with Java Practice MCQs

Question 1

Which JDK tool compiles .java source files into .class files?

Accepted Answer

D. javac

Answer

java

Answer

javadoc

Answer

jar

Answer

javac

Question 2

What does javac normally write into a .class file?

Accepted Answer

B. Platform-neutral JVM bytecode plus class metadata

Answer

Native machine code for the processor it was compiled on

Answer

Platform-neutral JVM bytecode plus class metadata

Answer

A copy of the source code with comments removed

Answer

Assembly language for the current operating system

Question 3

Which JVM component verifies, prepares and resolves a class (linking) and then initializes it, before any of its code runs?

Accepted Answer

A. Class loader subsystem

Answer

Class loader subsystem

Answer

Execution engine

Answer

JIT compiler

Answer

Garbage collector

Question 4

Which part of the Java platform contains development tools such as javac in addition to a runtime?

Accepted Answer

C. JDK

Answer

JRE

Answer

JVM

Answer

JDK

Answer

JIT

Question 5

What does the JVM's just-in-time (JIT) compiler do?

Accepted Answer

A. Translates frequently executed bytecode into native code while the program runs

Answer

Translates frequently executed bytecode into native code while the program runs

Answer

Converts .java source files into .class files before the program starts

Answer

Checks that loaded bytecode does not break the JVM's type-safety rules

Answer

Reclaims heap memory used by objects that are no longer reachable

Question 6

In Java 8, 11 or 17, which method declaration can the standard java launcher use as a program's entry point?

Accepted Answer

A. public static void main(String[] args)

Answer

public static void main(String[] args)

Answer

public void main(String[] args)

Answer

public static int main(String args)

Answer

private static void main(String[] args)

Question 7

Why is compiled Java code described as platform independent?

Accepted Answer

B. The same bytecode runs on any platform that provides a compatible JVM

Answer

javac produces one native executable that runs directly on every processor

Answer

The same bytecode runs on any platform that provides a compatible JVM

Answer

The JVM is a single binary file that runs unchanged on every operating system

Answer

Java programs are recompiled from source on each machine just before they run

Question 8

What is the range of values of a Java byte?

Accepted Answer

B. -128 to 127

Answer

-256 to 255

Answer

-128 to 127

Answer

-127 to 127

Answer

0 to 255

Question 9

What does a Java char value represent?

Accepted Answer

C. An unsigned 16-bit UTF-16 code unit

Answer

A signed 8-bit ASCII byte

Answer

Any complete Unicode character, including emoji

Answer

An unsigned 16-bit UTF-16 code unit

Answer

A 32-bit Unicode code point

Question 10

What does this program print?

```java
class Defaults {
    static int count;
    static double rate;
    static boolean flag;
    public static void main(String[] args) {
        System.out.println(count + " " + rate + " " + flag);
    }
}
```

Accepted Answer

D. 0 0.0 false

Answer

0 0 false

Answer

0 0.0 null

Answer

Compilation error: the fields are not initialized

Answer

0 0.0 false

Question 11

Which suffix must be added so that `long big = 8000000000;` compiles?

Accepted Answer

A. L

Answer

L

Answer

S

Answer

F

Answer

D

Question 12

What does the declaration `import java.util.ArrayList;` do?

Accepted Answer

D. Lets the source refer to java.util.ArrayList by its simple name

Answer

Copies the source code of ArrayList into the current file

Answer

Loads and initializes the ArrayList class as soon as the program starts

Answer

Gives the current class access to ArrayList's private members

Answer

Lets the source refer to java.util.ArrayList by its simple name

Question 13

Which setting tells java and javac where to search for user classes and JAR libraries?

Accepted Answer

D. The classpath (-cp or CLASSPATH)

Answer

The JAVA_HOME variable

Answer

The PATH variable

Answer

The javac -d option

Answer

The classpath (-cp or CLASSPATH)

Question 14

A method uses a variable name that was never declared. When is this reported?

Accepted Answer

C. At compile time, as a 'cannot find symbol' error

Answer

At runtime, as a NullPointerException

Answer

At class-loading time, as NoClassDefFoundError

Answer

At compile time, as a 'cannot find symbol' error

Answer

During bytecode verification, as a VerifyError

Question 15

Which of these is a reference type rather than one of Java's eight primitive types?

Accepted Answer

B. String

Answer

boolean

Answer

String

Answer

char

Answer

double

Object-Oriented Programming with Java Practice MCQs

Object-Oriented Programming with Java Free MCQs

Which JDK tool compiles .java source files into .class files?

What does javac normally write into a .class file?

Which JVM component verifies, prepares and resolves a class (linking) and then initializes it, before any of its code runs?

Which part of the Java platform contains development tools such as javac in addition to a runtime?

What does the JVM's just-in-time (JIT) compiler do?

In Java 8, 11 or 17, which method declaration can the standard java launcher use as a program's entry point?

Why is compiled Java code described as platform independent?

What is the range of values of a Java byte?

What does a Java char value represent?

What does this program print? ```java class Defaults { static int count; static double rate; static boolean flag; public static void main(String[] args) { System.out.println(count + " " + rate + " " + flag); } } ```

Which suffix must be added so that `long big = 8000000000;` compiles?

What does the declaration `import java.util.ArrayList;` do?

Which setting tells java and javac where to search for user classes and JAR libraries?

A method uses a variable name that was never declared. When is this reported?

Which of these is a reference type rather than one of Java's eight primitive types?

What does this code print? ```java int max = Integer.MAX_VALUE; // 2147483647 System.out.println(max + 1); ```

What does this code print? ```java char c = 'A'; System.out.println(c + 1); c++; System.out.println(c); ```

Two threads execute the same method at the same time. Which JVM runtime data area does each thread get its own separate copy of?

What does this program print? ```java public class Init { static int x = 5; static { x = x * 2; System.out.print("S" + x + " "); } public static void main(String[] args) { System.out.print("M" + x); } } ```

A file named Test.java contains only: ```java public class Hello { public static void main(String[] args) { } } ``` What happens when you run `javac Test.java`?

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