Java String Fundamentals Quiz
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Questions and Answers

What is the starting index of a character in a string in Java?

  • -1
  • 1
  • 2
  • 0 (correct)

    • Which statement correctly describes a String literal in Java?

  • A string literal is created using the new keyword.
  • A string literal cannot contain spaces.
  • A string literal is enclosed in single quotes.
  • A string literal is a series of characters in double quotes. (correct)

    • What does the String class's default constructor do?

  • Creates a null value reference.
  • Creates a string with a predefined value.
  • Creates a string with a value of 'null'.
  • Creates an empty string. (correct)

    • How many constructors does the String class have?

    <p>13</p> Signup and view all the answers

    What is the length of the string 'Hello World'?

    <p>11</p> Signup and view all the answers

    Which method can be used to create a String object from a string literal directly?

    <p>String greeting = &quot;Hello World!&quot;;</p> Signup and view all the answers

    What is stored in the heap area when a String object is created?

    <p>String objects and their values</p> Signup and view all the answers

    Which of the following statements correctly describes the use of the 'new' keyword when creating a String object?

    <p>It is used to create a String object with a given value.</p> Signup and view all the answers

    What does the method charAt() do in a string?

    <p>Returns the character at the specified index.</p> Signup and view all the answers

    What will be the output of the following code: System.out.println(strA.trim()); where strA is ' Program with care '?

    <p>Program with care</p> Signup and view all the answers

    When using the replace() method, what does the code strA.replace('b', 'c') do?

    <p>Changes all occurrences of 'b' to 'c'.</p> Signup and view all the answers

    What is the result of strA.equals(strB) if strA is 'Learn Java' and strB is also 'Learn Java'?

    <p>returns true</p> Signup and view all the answers

    What would be the output of System.out.println(strA.charAt(5)); if strA is 'Java Programming'?

    <p>P</p> Signup and view all the answers

    Which statement about the equals() method is true?

    <p>It returns true if both strings have the same characters in the same order.</p> Signup and view all the answers

    What does the method trim() specifically remove from a string?

    <p>Leading and trailing whitespace</p> Signup and view all the answers

    In the context of the replace() method, what does oldChar signify?

    <p>The character that will be replaced by newChar.</p> Signup and view all the answers

    What is the output of strA.indexOf('g') for the string 'It gets better'?

    <p>3</p> Signup and view all the answers

    What will strA.indexOf('t', 6) return for the string 'It gets better'?

    <p>10</p> Signup and view all the answers

    If strA.indexOf('gets', 7) is executed on the string 'It gets better', what will be the result?

    <p>-1</p> Signup and view all the answers

    What does the compareTo() method do in relation to two strings?

    <p>Compares strings based on alphabet order</p> Signup and view all the answers

    What is the purpose of the optional parameter fromIndex in the indexOf method?

    <p>To start searching from a specific index</p> Signup and view all the answers

    What does the syntax 'String str = new String(char chars[])' accomplish?

    <p>It creates a String object from an array of characters.</p> Signup and view all the answers

    What will be the output of this code: 'char chars[] = {'h', 'i', 's', 't', 'o','r','y'}; String s = new String(chars); System.out.println(s);'?

    <p>'history'</p> Signup and view all the answers

    What does the 'startIndex' parameter specify in the syntax 'String str = new String(char chars[], int startIndex, int count)'?

    <p>The index of the first character to be copied.</p> Signup and view all the answers

    In the syntax 'String str = new String(chars, 2, 3)', what does the count parameter indicate?

    <p>The number of characters to copy starting from the startIndex.</p> Signup and view all the answers

    Why is the variable 's' in the statement 'String s = new String(chars);' special?

    <p>It is a reference that points to a string in the heap.</p> Signup and view all the answers

    Which of the following correctly initializes a String object from a character array containing {'p', 'e', 'a', 'c', 'e', 'f', 'u', 'l'} starting at index 2 for a count of 3?

    <p>String str = new String({'p', 'e', 'a', 'c', 'e', 'f', 'u', 'l'}, 2, 3);</p> Signup and view all the answers

    What is the primary purpose of using packages in Java, as described in the content?

    <p>To organize multiple classes in a named collection.</p> Signup and view all the answers

    What will the line 'String str = new String(chars, 2, 3);' result in if chars[] is defined as {'e', 'f', 'g', 'h'}?

    <p>'fg'</p> Signup and view all the answers

    What does the method toLowerCase() do?

    <p>Converts all characters to lowercase.</p> Signup and view all the answers

    What does the method length() return?

    <p>The total number of characters in a string.</p> Signup and view all the answers

    What is the expected output of the following code: System.out.println(strB.concat(strA)); where strA = 'Java ' and strB = 'Programming'?

    <p>ProgrammingJava</p> Signup and view all the answers

    Which method would you use to find the position of the first occurrence of a character in a string?

    <p>string.indexOf()</p> Signup and view all the answers

    What will the call to 'strA.toLowerCase()' return if strA is initialized to 'HELLO'?

    <p>hello</p> Signup and view all the answers

    What parameters can be passed to indexOf() to find a character's index?

    <p>The character and an index to start searching from.</p> Signup and view all the answers

    What does the concat() method do in string manipulation?

    <p>Joins two strings together.</p> Signup and view all the answers

    If strA is 'TESTING', what will be the result of strA.toUpperCase()?

    <p>TESTING</p> Signup and view all the answers

    What does the method string.compareTo(String str) return when two strings are equal?

    <p>0</p> Signup and view all the answers

    What is the result of strA.compareTo(strC) if strA is 'Learn Java' and strC is 'Learn Kolin'?

    <p>-1</p> Signup and view all the answers

    How are elements in an array accessed in Java?

    <p>By using their index</p> Signup and view all the answers

    What is a requirement for the elements stored in an array in Java?

    <p>They must have the same data type</p> Signup and view all the answers

    What will happen to numeric array elements when they are created in Java without specific initialization?

    <p>They will default to 0</p> Signup and view all the answers

    In the example given, how many elements are declared in the array num?

    <p>6</p> Signup and view all the answers

    What is the starting index for accessing elements in a Java array?

    <p>0</p> Signup and view all the answers

    What does strC.compareTo(strA) return in the example provided?

    <p>1</p> Signup and view all the answers

    Study Notes

    Strings in Java

    • Strings are sequences of characters used extensively in Java programming
    • Java's String class handles string creation and manipulation
    • Characters within a string have numbered positions (index) starting at 0
    • String length is determined by the number of characters

    Creating Strings

    • Direct assignment: Assigning a string literal to a String object
      • String greeting = "Hello World!";
    • Using the new keyword and constructor: Creating a String object
      • String strGreet = new String("Hello World!");
    • String literals are enclosed in double quotes and considered constants
    • The compiler creates a String object when encountering a literal

    String Methods

    • charAt(int index): Returns the character at a specified index

    • equals(String str): Checks if two strings are identical in value

    • compareTo(String str): Compares strings lexicographically (dictionary order)

      • Returns 0 if equal, negative if comes before, positive if after

    • toLowerCase(): Converts all characters to lowercase

    • toUpperCase(): Converts all characters to uppercase

    • length(): Returns the number of characters in a string

    • concat(String str): Returns a new string by concatenating (joining) two strings

    • indexOf(int ch, int fromIndex): Finds the index of the first occurrence of a character, starting from an optional index

    Arrays in Java

    • Arrays store collections of elements of the same data type
    • Elements are accessed using an index (starting at 0)
    • Arrays hold a fixed number of elements
    • All elements are of the same data type: int, double, String, etc.
    • Arrays can be declared and initialized at the time of creation, or initialized by allocating memory space and then assigning data later
    • Arrays are stored in contiguous memory locations
    • Multi-dimensional: Arrays within arrays

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    Description

    Test your knowledge on Java String basics with this quiz. Questions cover String literals, constructors, and common methods such as charAt, trim, and replace. Perfect for beginners aiming to solidify their understanding of how Strings function in Java.

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