Java Strings and Methods
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Questions and Answers

Which part of the switch statement prevents the execution from falling through to the subsequent cases?

  • default
  • break (correct)
  • switch
  • case

What will happen if a case doesn't have a break statement?

  • The switch statement will terminate immediately.
  • The program will throw an error.
  • The statements of the next case will execute until a break is encountered. (correct)
  • The program will skip the switch statement.

What is the purpose of short-circuit evaluation in Java?

  • To always return true for logical expressions
  • To ensure that functions are executed multiple times
  • To evaluate all operands regardless of their values
  • To optimize performance by stopping evaluation once the result is clear (correct)

What happens when a break statement is omitted in a switch case?

<p>The flow of control falls through to the next case. (D)</p> Signup and view all the answers

Given the condition 'if (c == d || a == b)', what is the result when c = 4 and d = 4, a = 0, and b = 1?

<p>The condition evaluates to true and executes the statement (B)</p> Signup and view all the answers

In which of the following data types can a Java switch statement operate?

<p>char (A)</p> Signup and view all the answers

What will the following code print if temperature is set to 40? 'if (temperature >= 50) { if (temperature >= 110) { System.out.println(“hot”); } else { System.out.println(“warm”); } } else { System.out.println(“cold”); }'

<p>cold (C)</p> Signup and view all the answers

What is the purpose of the default case in a switch statement?

<p>To handle unexpected input when no case matches. (B)</p> Signup and view all the answers

Which statement is true about the switch statement?

<p>It executes exactly one block of code based on a variable's value (A)</p> Signup and view all the answers

Which of the following correctly describes the structure of a case in a switch statement?

<p>case value: code block (D)</p> Signup and view all the answers

In the expression 'if (a == b && c == d)', what happens when a equals b is false?

<p>The evaluation short-circuits and returns false without checking c == d (A)</p> Signup and view all the answers

What must be true for the value in a case statement to execute the corresponding block?

<p>It must match the switch variable's value. (C)</p> Signup and view all the answers

What would be the output of the following code if num is initialized to 0? 'while(num = 80) { System.out.println(“The grade is B”); }'

<p>An error will be thrown (D)</p> Signup and view all the answers

What is the implication of using a break statement within a default case?

<p>It can be omitted as no fall-through occurs from default. (A)</p> Signup and view all the answers

Which logical operator will stop evaluating once the left operand is true?

<p>|| (OR) (C)</p> Signup and view all the answers

Which is a consequence of using multiple cases without break statements?

<p>Unintentional execution of multiple case blocks. (C)</p> Signup and view all the answers

What should be the position of the default case within a switch statement?

<p>After the last case statement. (B)</p> Signup and view all the answers

Flashcards

Short-Circuit Evaluation

A process where a computer evaluates a logical expression from left to right, stopping as soon as the expression's value is determined.

Short-Circuit Operators

Logical AND (&&) and OR (||) operators that do not necessarily evaluate all their operands.

Logical AND (&&)

Returns true only if both operands are true; otherwise, it returns false.

Logical OR (||)

Returns true if at least one operand is true; otherwise, it returns false.

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Switch Statement

A statement that tests a single variable against multiple values to determine which block of statements to execute.

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if-else statement

A control flow statement in programming used to execute different code blocks based on whether a condition is true or false.

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Nested if-else statement

An if-else statement that is placed within another.

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Grade Calculation

Evaluates scores to assign corresponding letter grade (A,B,C,D,F).

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Switch Statement

A control flow statement that allows a program to select one of many code blocks based on the value of an expression.

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Switch Case

A labeled block of code within a switch statement. It specifies the value to be compared with the expression in the switch.

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Break Statement

A statement used to exit a switch statement or repetition structure when a match is found.

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Default Case

A block within a switch statement that is executed if none of the cases match the expression.

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Data Types Allowed in Switch Statement

In Java, the expression used in the switch statement can be int, byte, short, char, or String.

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Fall-through behavior

If no break statement is encountered after a match, the program execution continues into the next case.

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Reserved Keywords in Switch

Keywords like switch, case, break, and default are specifically used in switch statements.

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Switch statement

A control flow statement that executes different blocks of code depending on the value of an expression.

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Case label

A constant value within a switch statement that corresponds to a specific block of code.

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Default case

A block of code in a switch statement that is executed if none of the other cases match the expression's value.

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Break statement

A statement that exits a switch statement and transfers control to the statement following the switch.

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Char type variable

A variable that can store single character values, like 'A', 'B'.

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Switch expression

An expression that determines which of the possible cases should be executed.

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Control flow statement

A statement that regulates the order of execution of code.

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Study Notes

Java Strings

  • Strings are sequences of characters
  • Strings have methods for manipulation
  • Strings are objects, not primitive types
  • String length is the number of characters
  • Character position starts at index 0
  • Strings can be created directly or using new String()
  • String literals (e.g., "Hello World!") share memory
  • Constructed strings (using new) have separate memory
  • equals() compares string content, == compares references
  • Strings are immutable (cannot be changed after creation)

String Methods

  • charAt(index): Returns the character at the specified index
  • compareTo(string): Compares strings. Returns 0 if equal, < 0 if less, > 0 if greater
  • concat(string): Concatenates strings
  • equals(string): Returns true if strings have the same characters
  • equalsIgnoreCase(string): Returns true if strings have the same characters (case-insensitive)
  • indexOf(string): Returns the index of the first occurrence of a substring
  • lastIndexOf(string): Returns the index of the last occurrence of a substring
  • length(): Returns the length of the string
  • toLowerCase(): Returns a lowercase version of the string
  • toUpperCase(): Returns an uppercase version of the string
  • replace(oldChar, newChar): Replaces all occurrences of a character
  • substring(startIndex): Returns a substring from the start index to the end
  • substring(startIndex, endIndex): Returns a substring from startIndex to endIndex (exclusive of endIndex)
  • trim(): Removes leading and trailing whitespace

Control Structures (Repetition)

  • Java has while, for, and do-while loops
  • while: Executes a block of code while a condition is true
  • for: Repeats a block for a specific number of iterations
  • do-while: Executes a block at least once, then repeats while a condition is true
  • break: Exits the innermost loop or switch
  • continue: Skips the rest of the current iteration and starts the next
  • Nested loops are loops within loops

Control Structures (Selection)

  • Java uses if, if-else, and switch statements
  • if: Executes a block of code if a condition is true
  • if-else: Executes one block if a condition is true, another if it's false
  • switch: Executes different blocks depending on the value of an expression
  • break: Exits the switch statement

Short Circuit Evaluation

  • Logical expressions are evaluated efficiently, stopping when the outcome is known
  • && (AND) and || (OR) are short-circuit operators

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Strings Java PDF

Description

Explore the fundamental concepts of Java strings, including their properties and methods for manipulation. This quiz covers string creation, comparison, and key operations like concatenation and finding character positions. Understand the differences between string literals and constructed strings in Java.

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