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Questions and Answers
Which data structure in Java is a Last-In-First-Out (LIFO) data structure?
What is the primary characteristic of a Set in Java?
Which data structure in Java is a dynamic, heterogeneous collection of elements?
How do you access elements in an Array in Java?
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What operation is not supported by a Map in Java?
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What is the primary characteristic of a Queue in Java?
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What is the purpose of the break statement in a switch statement?
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What is the function of the default clause in a switch statement?
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What is the purpose of the else clause in an if-else statement?
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What is the result of the expression !(A && B) according to De Morgan's Laws?
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What is the function of the && operator in a conditional statement?
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What is the advantage of using short-circuit evaluation in conditional statements?
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Study Notes
Java Data Structures
Arrays
- A fixed-size, homogeneous collection of elements
- Declared using
[]syntax, e.g.int[] myArray; - Elements are accessed using an index, starting from 0
- Supports various operations, such as:
- Indexing:
myArray[0] - Length:
myArray.length - Iteration: using a for-each loop or a traditional for loop
- Indexing:
Lists
- A dynamic, heterogeneous collection of elements
- Implemented using the
ArrayListclass - Supports various operations, such as:
- Add:
myList.add(element) - Remove:
myList.remove(element) - Indexing:
myList.get(index) - Iteration: using a for-each loop or an iterator
- Add:
Sets
- A collection of unique elements, with no duplicates
- Implemented using the
HashSetclass - Supports various operations, such as:
- Add:
mySet.add(element) - Remove:
mySet.remove(element) - Contains:
mySet.contains(element) - Iteration: using a for-each loop or an iterator
- Add:
Maps
- A collection of key-value pairs, with unique keys
- Implemented using the
HashMapclass - Supports various operations, such as:
- Put:
myMap.put(key, value) - Get:
myMap.get(key) - Remove:
myMap.remove(key) - Contains:
myMap.containsKey(key) - Iteration: using a for-each loop or an iterator
- Put:
Stacks
- A Last-In-First-Out (LIFO) data structure
- Implemented using the
Stackclass - Supports various operations, such as:
- Push:
myStack.push(element) - Pop:
myStack.pop() - Peek:
myStack.peek()
- Push:
Queues
- A First-In-First-Out (FIFO) data structure
- Implemented using the
Queueinterface andLinkedListclass - Supports various operations, such as:
- Offer:
myQueue.offer(element) - Poll:
myQueue.poll() - Peek:
myQueue.peek()
- Offer:
Data Structures in Java
Arrays
- A fixed-size, homogeneous collection of elements
- Declared using
[]syntax, e.g.int[] myArray; - Elements are accessed using an index, starting from 0
- Supports indexing, length, and iteration operations
- Indexing:
myArray[0]to access the first element - Length:
myArray.lengthto get the total number of elements - Iteration: using a for-each loop or a traditional for loop
Lists
- A dynamic, heterogeneous collection of elements
- Implemented using the
ArrayListclass - Supports add, remove, indexing, and iteration operations
- Add:
myList.add(element)to add a new element - Remove:
myList.remove(element)to remove an element - Indexing:
myList.get(index)to access an element at a specific index - Iteration: using a for-each loop or an iterator
Sets
- A collection of unique elements, with no duplicates
- Implemented using the
HashSetclass - Supports add, remove, contains, and iteration operations
- Add:
mySet.add(element)to add a new element - Remove:
mySet.remove(element)to remove an element - Contains:
mySet.contains(element)to check if an element exists - Iteration: using a for-each loop or an iterator
Maps
- A collection of key-value pairs, with unique keys
- Implemented using the
HashMapclass - Supports put, get, remove, contains, and iteration operations
- Put:
myMap.put(key, value)to add a new key-value pair - Get:
myMap.get(key)to retrieve a value by its key - Remove:
myMap.remove(key)to remove a key-value pair - Contains:
myMap.containsKey(key)to check if a key exists - Iteration: using a for-each loop or an iterator
Stacks
- A Last-In-First-Out (LIFO) data structure
- Implemented using the
Stackclass - Supports push, pop, and peek operations
- Push:
myStack.push(element)to add a new element - Pop:
myStack.pop()to remove the top element - Peek:
myStack.peek()to retrieve the top element without removing it
Queues
- A First-In-First-Out (FIFO) data structure
- Implemented using the
Queueinterface andLinkedListclass - Supports offer, poll, and peek operations
- Offer:
myQueue.offer(element)to add a new element - Poll:
myQueue.poll()to remove the front element - Peek:
myQueue.peek()to retrieve the front element without removing it
If-Else Statements
- Used to execute a block of code when a condition is true and another block of code when it's false
- Syntax:
if (condition) {code to execute} else {code to execute} - Example:
if (x > 5) { System.out.println("x is greater than 5"); } else { System.out.println("x is less than or equal to 5"); }
Switch Statements
- Used to execute different blocks of code based on the value of an expression
- Syntax:
switch (expression) { case value1: code to execute; break;...default: code to execute; } - Expression: a value that is compared to the case values
- Case Values: constant values that are compared to the expression
- Break Statement: used to exit the switch statement
- Default Clause: optional clause that executes when no case value matches the expression
- Example:
int day = 2; switch (day) { case 1: System.out.println("Monday"); break; case 2: System.out.println("Tuesday"); break; default: System.out.println("Unknown day"); }
Nested Conditional Statements
- A conditional statement inside another conditional statement
- Used to evaluate multiple conditions and execute code based on their combinations
- Example:
if (x > 5) { if (y > 10) { System.out.println("x is greater than 5 and y is greater than 10"); } else { System.out.println("x is greater than 5 and y is less than or equal to 10"); } } else { System.out.println("x is less than or equal to 5"); }
Conditional Logic
- Logical Operators:
- AND (&&): true if both conditions are true
- OR (||): true if at least one condition is true
- NOT (!): true if the condition is false
- Short-Circuit Evaluation: the second operand is only evaluated if necessary
- Example:
if (x > 5 && y > 10) { System.out.println("x is greater than 5 and y is greater than 10"); } - De Morgan's Laws:
-
!(A && B)is equivalent to!A || !B -
!(A || B)is equivalent to!A && !B
-
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Description
Quiz about Java data structures, covering arrays and lists, including declaration, indexing, and operations.
