Questions and Answers
What is the correct way to define a new String?
What does the method length() do?
Finds the number of characters in a String.
What is the purpose of charAt(int index)?
Returns the char value at the specified index.
What does substring(int beginIndex, int endIndex) return?
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What does indexOf(int ch, int fromIndex) do?
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What does compareTo(String str) return?
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What does equals(String str) check?
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What is the purpose of the Scanner class?
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How do you define a Scanner object?
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How do you import the Scanner class?
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What does nextInt() do?
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What does nextDouble() return?
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What does next() do?
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What does nextLine() return?
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What is the Math class used for?
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What is Math.PI?
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What does sqrt() do?
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Study Notes
String Class Methods
-
Defining a New String:
- String variable can be initialized using
new String("text here")or simplyString variable = "text here";
- String variable can be initialized using
-
length() Method:
- Returns the number of characters in the string as an integer.
-
charAt(int index) Method:
- Retrieves the character at a specified index in the string and returns it as a char.
- Requires an integer parameter for the index.
-
substring(int beginIndex, int endIndex) Method:
- Returns a substring defined by a starting index (inclusive) and an ending index (exclusive).
- Can also create a substring from the starting index to the end of the string with
substring(int beginIndex).
-
indexOf(int ch, int fromIndex) Method:
- Finds the index of the first occurrence of a specified character, starting the search from a given index.
- Can also be used to search for a substring.
-
compareTo(String str) & compareToIgnoreCase(String str):
- Compares the original string with another string alphabetically.
- Returns a negative integer if the original comes before the other string, positive if it comes after, and zero if both are identical.
-
equals(String str) & equalsIgnoreCase(String str):
- Checks for equality between two strings.
- Returns true if the strings are identical, otherwise returns false.
- Requires a parameter that is the string to compare.
Scanner Class
-
Purpose:
- Facilitates easy input reading methods for various data types.
-
Defining Scanner Object:
- Instantiate using
Scanner reader = new Scanner(System.in);to read input from the console.
- Instantiate using
-
Importing Scanner Class:
- Include
import java.util.Scanner;before the class declaration to enable usage of the Scanner class.
- Include
-
nextInt() Method:
- Allows the user to input an integer value from the console and returns it as an int.
-
nextDouble() Method:
- Enables the user to input a double value, returning it as a double.
-
next() Method:
- Reads a single word input from the console and returns it as a String.
-
nextLine() Method:
- Retrieves an entire line of input from the console, including spaces, until a newline character is encountered.
Math Class
-
Overview:
- Contains static methods for basic numeric operations.
- Methods are callable on the class itself without needing to create an instance.
-
Math.PI:
- Constant that represents the value of π (pi) and is accessible without needing an object.
-
sqrt() Method:
- Computes the square root of a specified double value and returns it as a double.
- Requires a double parameter for the input value.
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Test your knowledge on the String and Scanner class methods with these flashcards. Each card covers important methods and definitions, ensuring you understand the fundamentals of string manipulation in programming.
