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Questions and Answers
What is a Java String?
What is a Java String?
- An interface for character sequences
- A sequence of characters
- A mutable class for creating characters
- An immutable class that represents a sequence of characters (correct)
The java.lang.String class implements the Serializable, Comparable, and CharSequence interfaces.
The java.lang.String class implements the Serializable, Comparable, and CharSequence interfaces.
True (A)
What does the CharSequence interface represent?
What does the CharSequence interface represent?
The sequence of characters
In Java, a String is mutable.
In Java, a String is mutable.
What is a Java String literal?
What is a Java String literal?
What does the NEW keyword do in Java?
What does the NEW keyword do in Java?
What are Java String references used for?
What are Java String references used for?
String objects in Java are mutable.
String objects in Java are mutable.
What is the purpose of the StringBuilder class?
What is the purpose of the StringBuilder class?
What does the StringBuilder append() method do?
What does the StringBuilder append() method do?
What does the StringBuilder insert() method do?
What does the StringBuilder insert() method do?
What does the StringBuilder replace() method do?
What does the StringBuilder replace() method do?
What is the function of the StringBuilder delete() method?
What is the function of the StringBuilder delete() method?
What does the StringBuilder reverse() method do?
What does the StringBuilder reverse() method do?
What does the StringBuilder capacity() method return?
What does the StringBuilder capacity() method return?
What is the purpose of the StringBuilder ensureCapacity() method?
What is the purpose of the StringBuilder ensureCapacity() method?
What does the StringBuilder getChars() method do?
What does the StringBuilder getChars() method do?
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Study Notes
Java Strings Overview
- Java String Class: Provides various methods for string operations, including compare(), concat(), equals(), split(), length(), replace(), compareTo(), intern(), and substring.
- Immutability: Java Strings are immutable; modifications create new instances instead of altering the existing one.
- Java String Literals: Created using double quotes, representing a fixed sequence of characters.
String and Character Representation
- String Object: In Java, a string is an object representing a sequence of characters.
- CharSequence Interface: Represents a sequence of characters; implemented by String and StringBuilder classes, allowing string creation through these classes.
String Objects and Usage
- String References: Store attributes like usernames and passwords, playing a crucial role in application programming.
- Immutable Strings: String objects cannot be modified post-creation, categorized as unmodifiable.
StringBuilder Class
- Mutable Strings: StringBuilder class allows creation of mutable strings, differing from StringBuffer by being non-synchronized.
- Key Methods:
- append(): Concatenates a specified argument to the current string.
- insert(): Inserts a specified string at a specified position.
- replace(): Replaces a substring defined by beginIndex and endIndex with a new string.
- delete(): Removes characters defined by beginIndex and endIndex.
- reverse(): Reverses the characters in the current string.
- capacity(): Returns the current capacity of the StringBuilder.
- ensureCapacity(): Ensures that the StringBuilder's capacity is at least a specified minimum.
- getChars(): Copies characters starting from a specified index into a given destination array.
Memory Management
- NEW Keyword: When using the NEW keyword to create Strings, two objects plus one reference variable are generated.
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