1. How are Java source code files named? A Java source code file takes the name of a public class or interface that is defined within the file. A source code file may contain at most one public class or interface. If a public class or interface is defined within a source code file, then the source code file must take the name of the public class or interface. If no public class or interface is defined within a source code file, then the file must take on a name that is different than its classes and interfaces. Source code files use the .java extension.
2. What is the relationship between the Canvas class and the Graphics class?
A Canvas object provides access to a Graphics object via its paint() method.
3. What are the high-level thread states?
The high-level thread states are ready, running, waiting, and dead.
4. What value does read() return when it has reached the end of a file?
The read() method returns -1 when it has reached the end of a file.
5. Can a Byte object be cast to a double value?
No, an object cannot be cast to a primitive value.
6. What is the difference between a static and a non-static inner class?
A non-static inner class may have object instances that are associated with instances of the class’s outer class. A static inner class does not have any object instances.
7. What is the difference between the String and StringBuffer classes?
String objects are constants. StringBuffer objects are not.
8. If a variable is declared as private, where may the variable be accessed?
A private variable may only be accessed within the class in which it is declared.
9. What is an object’s lock and which object’s have locks?
An object’s lock is a mechanism that is used by multiple threads to obtain synchronized access to the object. A thread may execute a synchronized method of an object only after it has acquired the object’s lock. All objects and classes have locks. A class’s lock is acquired on the class’s Class object.
10. What is the Dictionary class?
The Dictionary class provides the capability to store key-value pairs.
11. How are the elements of a BorderLayout organized?
The elements of a BorderLayout are organized at the borders (North, South, East, and West) and the center of a container.
12. What is the % operator?
It is referred to as the modulo or remainder operator. It returns the remainder of dividing the first operand by the second operand.
13. When can an object reference be cast to an interface reference?
An object reference be cast to an interface reference when the object implements the referenced interface.
14. What is the difference between a Window and a Frame?
The Frame class extends Window to define a main application window that can have a menu bar.
15. Which class is extended by all other classes?
The Object class is extended by all other classes.
16. Can an object be garbage collected while it is still reachable?
A reachable object cannot be garbage collected. Only unreachable objects may be garbage collected..
17. Is the ternary operator written x : y ? z or x ? y : z ?
It is written x ? y : z.
18. What is the difference between the Font and FontMetrics classes?
The FontMetrics class is used to define implementation-specific properties, such as ascent and descent, of a Font object.
19. How is rounding performed under integer division?
The fractional part of the result is truncated. This is known as rounding toward zero.
20. What happens when a thread cannot acquire a lock on an object?
If a thread attempts to execute a synchronized method or synchronized statement and is unable to acquire an object’s lock, it enters the waiting state until the lock becomes available.
2. What is the relationship between the Canvas class and the Graphics class?
A Canvas object provides access to a Graphics object via its paint() method.
3. What are the high-level thread states?
The high-level thread states are ready, running, waiting, and dead.
4. What value does read() return when it has reached the end of a file?
The read() method returns -1 when it has reached the end of a file.
5. Can a Byte object be cast to a double value?
No, an object cannot be cast to a primitive value.
6. What is the difference between a static and a non-static inner class?
A non-static inner class may have object instances that are associated with instances of the class’s outer class. A static inner class does not have any object instances.
7. What is the difference between the String and StringBuffer classes?
String objects are constants. StringBuffer objects are not.
8. If a variable is declared as private, where may the variable be accessed?
A private variable may only be accessed within the class in which it is declared.
9. What is an object’s lock and which object’s have locks?
An object’s lock is a mechanism that is used by multiple threads to obtain synchronized access to the object. A thread may execute a synchronized method of an object only after it has acquired the object’s lock. All objects and classes have locks. A class’s lock is acquired on the class’s Class object.
10. What is the Dictionary class?
The Dictionary class provides the capability to store key-value pairs.
11. How are the elements of a BorderLayout organized?
The elements of a BorderLayout are organized at the borders (North, South, East, and West) and the center of a container.
12. What is the % operator?
It is referred to as the modulo or remainder operator. It returns the remainder of dividing the first operand by the second operand.
13. When can an object reference be cast to an interface reference?
An object reference be cast to an interface reference when the object implements the referenced interface.
14. What is the difference between a Window and a Frame?
The Frame class extends Window to define a main application window that can have a menu bar.
15. Which class is extended by all other classes?
The Object class is extended by all other classes.
16. Can an object be garbage collected while it is still reachable?
A reachable object cannot be garbage collected. Only unreachable objects may be garbage collected..
17. Is the ternary operator written x : y ? z or x ? y : z ?
It is written x ? y : z.
18. What is the difference between the Font and FontMetrics classes?
The FontMetrics class is used to define implementation-specific properties, such as ascent and descent, of a Font object.
19. How is rounding performed under integer division?
The fractional part of the result is truncated. This is known as rounding toward zero.
20. What happens when a thread cannot acquire a lock on an object?
If a thread attempts to execute a synchronized method or synchronized statement and is unable to acquire an object’s lock, it enters the waiting state until the lock becomes available.
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