Strings are used in Java to express character sequences. They are often used in Java programming and are objects of the String class. The following are some significant Java string handling considerations.
Lets look at how to create strings:-
1.Creating a String:-
String message = "Hi!"
2.Concatenating String:-
String first = "Ball";
String second = "Pen";
String first with second = first + " " + second // "Ball Pen"
3.String Length:-
String product = "Mouse";
int length = product.length(); //5
4.To Access single character:-
String product = "Mouse";
char firstChar = product.charAt(0); //M
5.Comparing strings:-
String str1 = "Mango";
String str2 = "Grapes";
boolean isEqual = str1.equals(str2); //false
boolean isIgnoreCaseEqual = str1.equalsIgnoreCase(str2); //false
6.Substrings:-
String sentence = "Time is Money";
String substring = sentence.substring(7); //Money
7.String Manipulation:-
String str = "Money";
String upperCase = str.toUpperCase(); //"Money"
String str = "Money";
String lowerCase = str.toLowerCase(); //"money"
Lets see some code examples of Strings:-
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Questions and answers on Strings:-
Q1: What is a string in Java?
A1: In Java, a string is an object that represents a sequence of characters.
Q2: How do you declare a string variable in Java?
A2: You can declare a string variable by using the String keyword, like this: String str;
Q3: How do you initialize a string variable in Java?
A3: You can initialize a string variable by assigning a value to it, like this: String str = "Hello";
Q4: How do you find the length of a string in Java?
A4: You can use the 'length()' method of the String class to find the length of a string, like this: int length = str.length();
Q5: How do you concatenate two strings in Java?
A5: You can use the concatenation operator (+) to concatenate two strings, like this: String result = str1 + str2;
Q6: How do you compare two strings in Java?
A6: You can use the equals() method of the String class to compare two strings for equality, like this: boolean isEqual = str1.equals(str2);
Q7: How do you convert a string to uppercase in Java?
A7: You can use the toUpperCase() method of the String class to convert a string to uppercase, like this: String upperCaseStr = str.toUpperCase();
Q8: How do you convert a string to lowercase in Java?
A8: You can use the toLowerCase() method of the String class to convert a string to lowercase, like this: String lowerCaseStr = str.toLowerCase();
Q9: How do you check if a string contains a specific substring in Java?
A9: You can use the contains() method of the String class to check if a string contains a specific substring, like this: boolean containsSubstring = str.contains(substring);
Q10: How do you extract a substring from a string in Java?
A10: You can use the substring() method of the String class to extract a substring from a string, like this: String substring = str.substring(startIndex, endIndex);
Q11: How do you split a string into an array of substrings in Java?
A11: You can use the split() method of the String class to split a string into an array of substrings based on a delimiter, like this: String[] substrings = str.split(delimiter);
Q12: How do you remove leading and trailing whitespace from a string in Java?
A12: You can use the trim() method of the String class to remove leading and trailing whitespace from a string, like this: String trimmedStr = str.trim();
Q13: How do you replace a specific character or substring in a string in Java?
A13: You can use the replace() method of the String class to replace a specific character or substring in a string, like this: String replacedStr = str.replace(oldValue, newValue);
Q14: How do you check if a string starts with a specific prefix in Java?
A14: You can use the startsWith() method of the String class to check if a string starts with a specific prefix, like this: boolean startsWithPrefix = str.startsWith(prefix);
Q15: How do you check if a string ends with a specific suffix in Java?
A15: You can use the endsWith() method of the String class to check if a string ends with a specific suffix, like this: boolean endsWithSuffix = str.endsWith(suffix);
Q16:How do you convert a string to an integer in Java?
A16: You can use the parseInt() method of the Integer class to convert a string to an integer like this: int intValue = Integer.parseInt(str);
Q17: How do you convert an integer to a string in Java?
A17: You can use the toString() method of the Integer class to convert an integer to a string, like this: String strValue = Integer.toString(intValue);
Q18: How do you check if a string is empty in Java?
A18: You can use the isEmpty() method of the String class to check if a string is empty, like this: boolean isEmpty = str.isEmpty();
Q19: How do you check if a string is null in Java?
A19: You can use the == operator to check if a string is null, like this: boolean isNull = str == null;
Q20: How do you iterate over each character in a string in Java?
A20: You can use a for loop to iterate over each character in a string, like this:
for (int i = 0; i < str.length(); i++) {
char c = str.charAt(i);
// do something with the character
}
Q21: How do you convert a string to a character array in Java?
A21: You can use the toCharArray() method of the String class to convert a string to a character array, like this: char[] charArray = str.toCharArray();
Q22: How do you check if a string contains only numeric characters in Java?
A22: You can use the matches() method of the String class with a regular expression to check if a string contains only numeric characters, like this: boolean isNumeric = str.matches("\\d+");
Q23: How do you reverse a string in Java?
A23: You can use a StringBuilder or StringBuffer to reverse a string, like this:
StringBuilder reversedStr = new StringBuilder(str);
reversedStr = reversedStr.reverse();
Q24: How do you convert a string to a double in Java?
A24: You can use the parseDouble() method of the Double class to convert a string to a double, like this: double doubleValue = Double.parseDouble(str);
Q25: How do you convert a double to a string in Java?
A25: You can use the toString() method of the Double class to convert a double to a string, like this: String strValue = Double.toString(doubleValue);
Q26: How do you remove all occurrences of a specific character from a string in Java?
A26: You can use the replace() method of the String class to remove all occurrences of a specific character from a string, like this: String replacedStr = str.replace(character, "");
Q27: How do you check if a string is a palindrome in Java?
A27: You can compare the string with its reversed form to check if it is a palindrome, like this:
String reversedStr = new StringBuilder(str).reverse().toString();
boolean isPalindrome = str.equals(reversedStr);
Q28: How do you check if a string contains only alphabetic characters in Java?
A28: You can use the matches() method of the String class with a regular expression to check if a string contains only alphabetic characters, like this: boolean isAlphabetic = str.matches("[a-zA-Z]+");
Q29: How do you check if a string is a valid email address in Java?
A29: You can use the matches() method of the String class with a regular expression to check if a string is a valid email address, like this: boolean isEmail = str.matches("[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\\.[a-zA-Z]{2,}");
Q30: How do you convert a string to a date in Java?
A30: You can use the SimpleDateFormat class to convert a string to a date, like this:
SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd");
Date date = dateFormat.parse(str);
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