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?

The flow of control falls through to the next case. 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?

The condition evaluates to true and executes the statement Signup and view all the answers

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

char 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”); }'

cold Signup and view all the answers

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

To handle unexpected input when no case matches. Signup and view all the answers

Which statement is true about the switch statement?

It executes exactly one block of code based on a variable's value Signup and view all the answers

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

case value: code block Signup and view all the answers

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

The evaluation short-circuits and returns false without checking c == d Signup and view all the answers

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

It must match the switch variable's value. 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”); }'

An error will be thrown Signup and view all the answers

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

It can be omitted as no fall-through occurs from default. Signup and view all the answers

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

|| (OR) Signup and view all the answers

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

Unintentional execution of multiple case blocks. Signup and view all the answers

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

After the last case statement. Signup and view all the answers

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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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.