CUET Information practice (IP) Chapter 3 Java Programming Fundamentals (Revision Tour-I)

(c)

Explanation- GUI is built from GUI components known as control. A GUI component is an object with which the user interacts.

(a)

Explanation- GUI builder is also called Design area or Design space. It is the place where GUI design takes place in the IDE.

(d)

Explanation- The Palette contains all the components needed to create GUI application. It includes the icons of various types of controls available under Java Swing API.

(a)

Explanation- First, a container control is drawn as it can hold other controls within it. Then controls are drawn inside the container known as child controls.

(b)

Explanation- A user invokes the button by clicking over it and then action event gets activated.

(b)

Explanation- We can use this event (KeyEvent) to watch for specific keystrokes entered by the user.

(d)

Explanation- The characters that cannot be typed directly from the keyboard are called non-graphic characters. These can be represented by using escape sequences.

(b)

Explanation- Java programs display characters from the Unicode character set.

(a)

Explanation- The Swing components that support getText() method includes: TextField, TextArea, Button, Label etc.

(b)

Explanation- With the JLabel class, we can display unselectable text and images.

(a)

Explanation- A lightweight component directly implements the look-and-feel of the component in Java rather than delegating the look-and-feel to a native peer. Lightweight components can be more efficient at utilizing system resource and can be transparent.

(a)

Explanation- Java compiler compiles the Java source code files (*.java) into binary files (*.class). Java bytecode is the form of instructions that the Java virtual machine executes.

(d)

Explanation- The ContainerEvent class extends from the ComponentEvent class. This is a low-level event that is generated when container's contents change because of addition or removal of components.

(a)

Explanation- ‘=’ is used to assign a value. For example, value = 5 assigns 5 to value.

(c)

Explanation- It is an application program consisting of different development tools needed for developing an application.

(b)

Explanation- Java Virtual Machine is an abstract machine that is implemented on the top of the existing processors.

(a)

Explanation- Rapid development of application is possible through RAD tools.

(b)

Explanation- The ActionListener interface must be implemented to capture an ActionEvent. This interface provides processAction () method, which is called when the ActionEvent for which the ActionListener is registered occurs.

(a)

Explanation- Whenever we click a mouse button, move the mouse or type on the computer keyboard, we are generating what is referred to as an event.

(b)

Explanation- The components that we use for creating a GUI in Java are available through Swing API.

(b)

Explanation- Abstract Window Toolkit is a basic GUI toolkit of Java platform. Swing internally borrows functionality from AWT.

(a)

Explanation- Java compiler compiles the Java source code files (*.java) into binary files (*.class). Java bytecode is the form of instructions that the Java virtual machine executes.

(b)

Explanation- GUI components include container control and child control. These controls can be drawn on forms/windows/frames.

(b)

Explanation- A user invokes the button by clicking over it and then Action Event gets activated.

(d)

Explanation- The Java byte code looks a lot like machine language. It is a machine instruction for a Java processor chip called Java Virtual Machine.

(c)

Explanation- A software message indicating that something has happened such as a keystroke or mouse click.

(d)

Explanation- Java programs can run on any platform. This is because java code is first converted to byte code, which is platform independent. Then it is translated into the native language of host machine using interpreter.

(a)

Explanation- Real literals are numbers having fractional parts.

(b)

Explanation- The variables storing memory addresses are known as reference variables and their data type is known as reference data type.

(a)

Explanation- Variables represent named storage locations whose values can be manipulated.

(c)

(d)

Explanation- These are the characteristics or properties. Its behaviour is: it takes rest, it attends lectures etc.

(d)

Explanation- In the above expression, first && operator executes, followed by ||. Thus, the result 1 is obtained which corresponds to true.

(a)

Explanation- Literals are data items that never change their value during a program run. They are integer constant, character-constant, floating constant and string–literal.

(a)

Explanation- Keywords are the words that convey a special meaning to a language compiler. They cannot be used as identifier names.

(a)

Explanation: Every unit that makes a sentence in java is a token.

(d)

Explanation- The tokens are: Keywords, Identifiers, Literals, Punctuators and Operators.

(a)

Explanation- At first, the Java source code (in .java files) is compiled into Bytecode. When the Java application is started, the Bytecode is interpreted by the Java Virtual Machine.

(a)

Explanation- The JTextArea class provides a component that displays multiple lines of text and optionally allows the user to edit the text. If you need to obtain only one line of input from the user, you should use a text field.

(c)

Explanation: The above code takes the value of k less than n, i.e., while k<12, the code executes and add 1 when k=11.

(d)

Explanation: Variables represent named storage locations; they hold a data value of a particular data type. Here, table is a variable that refers to an array type.

(b)

Explanation- Selection statements are used in a program to choose different paths of execution based upon the outcome of an expression or the state of a variable. Java supports two selection statements: if and switch.

(a)

Explanation- Iteration statements enable program execution to repeat one or more statements, i.e., iteration statements form loops. In Java, there are three iteration statements: for, while and do.

(c)

Explanation- Jump statements are used to unconditionally transfer the program control to another part of the program. Java has three jump statements: break, continue, and return.

(a)

Explanation- The switch statement executes by comparing the value of the expression with each of the constants after the case statements. If a match is found, the statements following that case statement are executed. Otherwise the statements following the default statement (if present) are executed. Conventionally, the default label is put after all the case labels but it may appear anywhere in the block.

(d)

Explanation- for loop is the most versatile looping construct. It is used to continuously execute a block of code until a particular condition is satisfied. It comprises three parts: initialization, condition and iteration.

(c)

Explanation- Java offers an assignment operator=, to assign one value to another, e.g., int x=10;

(b)

Explanation- Like other programming languages, Java offers an assignment operator =, to assign value to a variable. Example, int x=1;

(a)

Explanation- The long data type is a 64-bit signed two's complement integer. It has a minimum value of -9,223,372,036,854,775,808 and a maximum value of 9,223,372,036,854,775,807 (inclusive). We Use this data type when we need a range of values wider than those provided by int.

(c)

Explanation- The syntax to declare a new variable is to write the specifier of the desired data type (like int,..) followed by a valid variable identifier. For example, int number = 2;

(b)

Explanation- 45 / 4 is an integer division, which results in 11.

(d)

Explanation- 2 % 1 is 0, 15 % 4 is 3, 25 % 5 is 0 and 37 % 6 is 1.

(d)

Explanation- Operands are evaluated from left to right in Java. The left-hand operand of a binary operator is evaluated before any part of the right-hand operand is evaluated. This rule takes precedence over any other rules that govern expressions. Therefore, ++j is evaluated first, and returns 1. Then j*5 is evaluated, so i=6.

(c)

Explanation- When evaluating x++ + x, x++ is evaluated first, returns 1 since it is post-increment. x becomes 2. Therefore, y is 1 + 2.

(b)

Explanation- When evaluating x + x++, x is evaluated first, which is 1. X++ returns 1 since it is post-increment and 2. Therefore, y is 1 + 1.

(d)

Explanation- The double data type is a double-precision 64-bit floating point. It covers a range from 4.94065645841246544e-324d to 1.79769313486231570e+308d (positive or negative).

(b)

Explanation- Java characters use Unicode encoding. Unicode is a two-byte character code set that has characters representing almost all characters.

(a)

Explanation- Floating point describes a system for representing numbers that would be too large or too small to be represented as integers. Numbers in general are represented approximately to a fixed number of significant digits and scaled using an exponent. The base for the scaling is normally 2, 10 or 16. The typical number that can be represented exactly is of the form:

significant digits × base^exponent

(b)

Explanation- An infinite loop is a sequence of instructions in a computer program, which loops endlessly either due to the loop having no terminating condition, having one that can never be met or one that causes the loop to start over.

(b)

Explanation- With the JLabel class, we can display unselectable text and images.

(a)

Explanation- A Swing component is a self-contained graphic entity that can be customized and inserted into applications. For example, Jlabel, Jbutton etc.

(d)

Explanation- Basic Swing Controls are simple components that are used primarily to get input from the user.

(c)

Explanation- A list is a component that performs basically the same function as a combo box but it enables the user to choose a single value or multiple values.

(c)

Explanation- AWT Components are called heavyweight components because of their dependency on native libraries. Swing components are called lightweight due to their independence of native libraries. Hence, Swing operations are much faster.

(b)

Explanation- A container is a component that holds other components. The base class for all containers is java.awt.Container, which is a subclass of java.awt.Component.

(a)

Explanation- Event-driven programs do not have a set sequence of instructions to execute. They also do not have a predetermined finish. The most common example of event-driven programming is found in graphical user interfaces (GUIs).

(b)

Explanation- The Abstract Window Toolkit (AWT) is a package of JDK classes for creating GUI components such as buttons, menus and scrollbars for applets and standalone applications.

(c)

Explanation- A GUI program consists of three types of software:Graphical components make up the Graphical User Interface. Listener methods receive the events and respond to them. Application methods do useful work for the user.

(a)

Explanation- Window is a visual area containing some kind of user interface. Windows are primarily associated with graphical displays, where they can be manipulated with a mouse cursor.

(d)

Explanation- A container is a component, which allows a Container object to be placed inside another Container object. For example, a Panel is a Container and a Frame is a Container. Panel is also a Component so it can be placed inside a Frame.

(a)

Explanation: Every component broadcasts events when a user interacts with it. When a user clicks a Button, e.g., it dispatches a MouseEvent.CLICK event and when a user selects an item in a List, the List dispatches an Event.CHANGE event.

(c)

Explanation- A listener is called when the user does something to the user interface that causes an event. Listener methods are a kind of call back; they are triggered when a form is submitted or a link is clicked.

(d)

Explanation- With the exception of top-level containers, all Swing components whose names begin with "J" descend from the JComponent class. For example, JPanel, JScrollPane, JButton and JTable all inherit from JComponent. The JComponent class extends the Container class, which itself extends Component.

(b)

Explanation- Increment the variable by one; evaluates to the value of variable before it was incremented.

(d)

Explanation: +value is incremented by 1, before it is evaluated, i.e., value =1 and similarly, count is incremented by 1.

(d)

Explanation- ++count is evaluated after it is incremented. Hence, int count becomes 2 and assigned to value.

(c)

Explanation- operator(--op) decrements op by 1. In this case, variable b is decremented by 1 and then assigned to variable a. Hence, a=9 and b=9.

(c)

Explanation- A double variable usually uses 64 bits to store its value. This primitive type store fractional number.

(a)

Explanation- Java has well-defined rules for specifying the order in which the operators in an expression are evaluated when the expression has several operators. Operator precedence determines the order in which expressions are evaluated.

(b)

Explanation- Java has well-defined rules for specifying the order in which the operators in an expression are evaluated when the expression has several operators. For example, multiplication and division have a higher precedence than addition and subtraction. Precedence rules can be overridden by explicit parentheses.

(a)

Explanation- In a program, statements may be executed sequentially, selectively or iteratively. A common type of program loop that is controlled by an integer that counts up from an initial value to an upper limit. Such a loop is called a counting loop. In a Sentinel-Controlled loop, a special value called a sentinel value is used to change the loop control expression from true to false. Example while loop. A result-controlled loop keeps looping until the computation has reached a particular goal.

(b)

Explanation- First initialization expression is executed, i.e., j=0 which gives the first value 1 to variable j. Then the test expression is evaluated, i.e., j<5 which results into true. Since the test expression is true, the body of the loop is executed, after executing the loop body, the update expression j++ is executed, which increments the value of j. After the update expression is executed, the test expression is again evaluated and sequence is repeated otherwise the loop is terminated (when j=5.

(d)

Explanation- First initialization expression is executed, i.e., j=10 which gives the first value 10 to variable j. Then the test expression is evaluated, i.e., j>5 which results into true. Since the test expression is true, the body of the loop is executed, after executing the loop body, the update expression j-- is executed, which decrements the value of j. After the update expression is executed, the test expression is again evaluated and sequence is repeated, otherwise the loop is terminated (when j=5.

(b)

Explanation- Update expression is required after the test expression, so that the values of loop variable changes. J=j+2 will increment the value of j by 2 and give the required output.

(d)

Explanation- First initialization expression is executed, i.e., j=5 which gives the first value 5 to variable j. Then the test expression is evaluated, i.e., j>-5 which results into true. Since the test expression is true, the body of the loop is executed, after executing the loop body, the update expression j-- is executed, which decrements the value of j. After the update expression is executed, the test expression is again evaluated and sequence is repeated, otherwise the loop is terminated (when j>-5.

(a)

Explanation- The value placed in var is 0 as 12 is greater than 9; so, first value is placed in var else if the condition has been false than the second value would be placed is var.

(c)

Explanation- (19-5=14 > (5-19=-14 ? 14:-14, results in 14>-14; so, the first value is assigned to p, i.e., p=14.

(c)

Explanation-choice=(5>10&&5>15?5:(10>15?10:15

In(10>15?10:15expression, condition is false so the result is 15, similarly in (5>10&&5>15 the condition is false; so, the result is 15.

(d)

Explanation- sum += price>=100 results in sum+=100 and price *1.1 = 110:100 since the first condition is true; therefore, sum=10+110, i.e., 120.

(a)

Explanation- do-while is an exit controlled loop, it evaluates its test expression at the bottom of the loop. The statement is executed from count 10 and terminates when count is less than 5.

(b)

Explanation- Loops implemented with the test at the bottom (a do loop) are called bottom-driven loops.

(b)

Explanation- Branching statements allow different sections of code to be executed or not to be executed depending on some condition either being true or false. For example, if, if .. else, while, do, switch and for constructs.

(a)

Explanation- A block is a sequence of statements, local class declarations and local variable declaration statements within braces.

(d)

Explanation- The above code initializes the variable by 0. Test expression is evaluated, i.e., count<=20, which is true then loop is executed and expression is updated, i.e., incremented by 2. Loop terminates when count =20.

(a)

Explanation- An event in Java is represented as an object. When the user generates an event, the Java system creates an event object. The event object is then sent to the listener that has been registered for the GUI component.

(a)

Explanation- An event listener is an object to which a component has delegated the task of handling a particular kind of event. In other words, if we want an object in the program to respond to another object, which is generating events; we must register object with the event generating object and then handle the generated events when it comes.

(c)

Explanation- In Swing, classes that represent GUI components have names beginning with the letter J. Some examples are JButton, JLabel and JSlider.

(d)

Explanation- The JComponent class of the javax.swing package serves as the base class.

(c)

Explanation- do-while loop is always executed at least once. It evaluates its test-expression at the bottom of the loop after executing its loop-body statements.

(b)

Explanation- Break is a keyword that breaks out of the code block, usually surrounded by braces, which it is in. Break prevents the program from falling through and executing the code in all the other case statements.