18 Questions
What is the implication of increasing the size of a matrix in terms of wastage space?
It will increase the wastage space.
In Java, what is a string?
In Java, string is basically an object that represents a sequence of char values.
How can you create a Java String object?
By string literal or by using the new keyword.
What is the difference between String and StringBuffer/StringBuilder classes in Java?
String class is immutable while StringBuffer and StringBuilder classes are mutable.
How is a Java String literal created?
By using double quotes.
What happens when a new Java String literal is created?
The JVM checks the 'string constant pool' first.
What is the difference between creating a string using Java string literal and using the new keyword?
Java string literal does not create a new instance if the value already exists in the string constant pool, while using the new keyword always creates a new object.
How does JVM handle string objects created using Java string literals and the new keyword?
JVM creates a new string object in heap memory for new keyword usage, while it checks the string constant pool for literals and may return the reference if the value already exists.
What happens when a string object with a specific value is not found in the string constant pool?
JVM creates a new object for that value in heap memory.
How can you create a string in Java using a character array?
By using the constructor new String(char[] ch).
What is an algorithm?
An algorithm is a step-by-step procedure or set of rules for solving a computational problem or performing a task.
How would you represent a sparse matrix in data structures?
Sparse matrix can be represented efficiently using linked lists.
Define a sparse matrix.
A matrix with a larger number of zero elements than non-zero elements.
How can non-zero elements in a sparse matrix be stored?
Using triplets that represent rows, columns, and values.
What are the two ways to represent a sparse matrix?
Array and LinkedList.
What are the three fields used in the 2D array representation of a sparse matrix?
Row, Column, Value.
What is the purpose of Row field in a sparse matrix representation?
To indicate the index of the row where a non-zero element is located.
How can a sparse matrix be visualized?
As a grid with many zero elements and fewer non-zero elements.
Study Notes
Java Strings
- A string in Java is an object that represents a sequence of characters.
- An array of characters works similarly to a Java string.
- Java String class provides various methods to perform operations on strings, such as compare(), concat(), equals(), split(), length(), replace(), compareTo(), intern(), and substring().
- Java String is immutable, meaning it cannot be changed, and a new instance is created whenever a string is changed.
- For mutable strings, StringBuffer and StringBuilder classes can be used.
Creating String Objects
- There are two ways to create a String object: by string literal and by using the new keyword.
- String literal is created by using double quotes, and the JVM checks the "string constant pool" first to avoid creating duplicate instances.
- When creating a string using the new keyword, a new string object is created in the heap memory, and the literal is placed in the string constant pool.
String Example
- The code snippet demonstrates creating strings using literals and the new keyword, and converting a char array to a string.
String Class Inbuilt Functions
- Various inbuilt functions are available in the String class, such as length(), concat(), and substring(), among others.
Algorithm and Arrays
- An algorithm is a step-by-step procedure for solving a computational problem or performing a task.
- In Java, arrays can be declared using int[] Array or int Array[].
- A 2D array can be declared as int mat[][] = new int.
2D Array - Matrix
- A matrix can be defined as a 2D array having 'm' rows and 'n' columns.
- A matrix with m rows and n columns is called an m × n matrix.
Sparse Matrix
- A sparse matrix is a matrix that has a greater number of zero elements than non-zero elements.
- The non-zero elements in a sparse matrix can be stored using triplets: rows, columns, and values.
- There are two ways to represent a sparse matrix: array and linklist.
- In 2D array representation, three fields are used: row, column, and value.
Test your knowledge on Java String class and operations like compare, concat, split, length, replace, compareTo, and more. Understand how an array of characters works similarly to a Java string.
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