Java String Methods PDF

JAVA STRING METHODS Java provides a wide range of methods for working with String objects. 1. length()  Description: Returns the length of the string. String str = "Hello, World!"; int length = str.length(); System.out.println(length); // Output: 13 2. charAt(int index...

JAVA STRING METHODS Java provides a wide range of methods for working with String objects. 1. length()  Description: Returns the length of the string. String str = "Hello, World!"; int length = str.length(); System.out.println(length); // Output: 13 2. charAt(int index)  Description: Returns the character at the specified index. String str = "Hello"; char ch = str.charAt(1); System.out.println(ch); // Output: 'e' 3. substring(int beginIndex)  Description: Returns a new string that is a substring starting from the specified index. String str = "Hello, World!"; String sub = str.substring(7); System.out.println(sub); // Output: "World!" 4. substring(int beginIndex, int endIndex)  Description: Returns a substring from beginIndex to endIndex - 1. String str = "Hello, World!"; String sub = str.substring(0, 5); System.out.println(sub); // Output: "Hello" 5. contains(CharSequence sequence)  Description: Checks if the string contains the specified character sequence. String str = "Hello, World!"; boolean contains = str.contains("World"); System.out.println(contains); // Output: true 6. equals(Object another)  Description: Compares the string to the specified object for equality. String str1 = "Hello"; String str2 = "Hello"; boolean isEqual = str1.equals(str2); System.out.println(isEqual); // Output: true 7. equalsIgnoreCase(String another)  Description: Compares two strings, ignoring case differences. String str1 = "HELLO"; String str2 = "hello"; boolean isEqual = str1.equalsIgnoreCase(str2); System.out.println(isEqual); // Output: true 8. indexOf(String str)  Description: Returns the index of the first occurrence of the substring. String str = "Hello, World!"; int index = str.indexOf("World"); System.out.println(index); // Output: 7 9. indexOf(String str, int fromIndex)  Description: Returns the index of the first occurrence of the substring starting from the specified index. String str = "Hello, World! World!"; int index = str.indexOf("World", 8); System.out.println(index); // Output: 14 10. lastIndexOf(String str)  Description: Returns the index of the last occurrence of the substring. String str = "Hello, World! World!"; int lastIndex = str.lastIndexOf("World"); System.out.println(lastIndex); // Output: 14 11. toUpperCase()  Description: Converts all characters in the string to uppercase. String str = "hello"; String upper = str.toUpperCase(); System.out.println(upper); // Output: "HELLO" 12. toLowerCase()  Description: Converts all characters in the string to lowercase. String str = "HELLO"; String lower = str.toLowerCase(); System.out.println(lower); // Output: "hello" 13. trim()  Description: Removes leading and trailing whitespace. String str = " Hello, World! "; String trimmed = str.trim(); System.out.println(trimmed); // Output: "Hello, World!" 14. replace(char oldChar, char newChar)  Description: Replaces all occurrences of a specified character with a new character. String str = "hello"; String newStr = str.replace('l', 'p'); System.out.println(newStr); // Output: "heppo" 15. replace(CharSequence target, CharSequence replacement)  Description: Replaces all occurrences of a substring with another substring. String str = "Hello, World!"; String newStr = str.replace("World", "Java"); System.out.println(newStr); // Output: "Hello, Java!" 16. split(String regex)  Description: Splits the string into an array based on the given regular expression. String str = "apple,orange,banana"; String[] fruits = str.split(","); for (String fruit : fruits) { System.out.println(fruit); } // Output: // apple // orange // banana 17. split(String regex, int limit)  Description: Splits the string into an array, with a maximum number of substrings. String str = "apple,orange,banana"; String[] fruits = str.split(",", 2); for (String fruit : fruits) { System.out.println(fruit); } // Output: // apple // orange,banana 18. startsWith(String prefix)  Description: Checks if the string starts with the specified prefix. String str = "Hello, World!"; boolean starts = str.startsWith("Hello"); System.out.println(starts); // Output: true 19. endsWith(String suffix)  Description: Checks if the string ends with the specified suffix. String str = "Hello, World!"; boolean ends = str.endsWith("World!"); System.out.println(ends); // Output: true 20. isEmpty()  Description: Checks if the string is empty (length is 0). String str = ""; boolean empty = str.isEmpty(); System.out.println(empty); // Output: true 21. join(CharSequence delimiter, CharSequence... elements)  Description: Joins multiple strings with the specified delimiter. String date = String.join("-", "2024", "10", "20"); System.out.println(date); // Output: "2024-10-20" 22. compareTo(String anotherString)  Description: Compares two strings lexicographically. String str1 = "apple"; String str2 = "banana"; int result = str1.compareTo(str2); System.out.println(result); // Output: negative value (because "apple" < "banana") 23. compareToIgnoreCase(String anotherString)  Description: Compares two strings lexicographically, ignoring case differences. String str1 = "apple"; String str2 = "Banana"; int result = str1.compareToIgnoreCase(str2); System.out.println(result); // Output: negative value 24. valueOf(int i)  Description: Converts a given value (e.g., int, long, float, boolean) to a string. int num = 123; String strValue = String.valueOf(num); System.out.println(strValue); // Output: "123" 25. toCharArray()  Description: Converts the string to a new character array. String str = "Hello"; char[] chars = str.toCharArray(); for (char ch : chars) { System.out.println(ch); } // Output: // H // e // l // l // o JAVA TYPE CASTING Type casting or type conversion, and it can be either implicit (automatic) or explicit (manual). 1. String to Integer (String to int) You can convert a String that represents a number to an int using Integer.parseInt() or Integer.valueOf(). String str = "123"; int num = Integer.parseInt(str); // Using parseInt() int num2 = Integer.valueOf(str); // Using valueOf() System.out.println(num); // Output: 123 2. Integer to String (int to String) You can convert an int to a String using String.valueOf() or Integer.toString(). int num = 123; String str = String.valueOf(num); // Using String.valueOf() String str2 = Integer.toString(num); // Using Integer.toString() System.out.println(str); // Output: "123" 3. String to Double (String to double) Convert a String to a double using Double.parseDouble(). 4. Double to String (double to String) You can convert a double to a String using String.valueOf(). 5. String to Float (String to float) Convert a String to a float using Float.parseFloat(). 6. Float to String (float to String) You can convert a float to a String using String.valueOf(). 7. String to Long (String to long) Convert a String to a long using Long.parseLong(). 8. Long to String (long to String) Convert a long to a String using String.valueOf(). 9. String to Boolean (String to boolean) Convert a String to a boolean using Boolean.parseBoolean(). 10. Boolean to String (boolean to String) Convert a boolean to a String using String.valueOf(). 11. Int to Double (int to double) (Implicit Conversion) An int can be converted to a double automatically by Java because double is a larger data type. int num = 5; double d = num; // Implicit conversion System.out.println(d); // Output: 5.0 12. Double to Int (double to int) (Explicit Conversion) To convert a double to an int, you need to use explicit casting. double d = 5.99; int num = (int) d; // Explicit cast System.out.println(num); // Output: 5 13. Int to Float (int to float) (Implicit Conversion) An int can be converted to a float automatically. 14. Float to Int (float to int) (Explicit Conversion) You can convert a float to an int using explicit casting. 15. Char to Int (char to int) You can convert a char to an int (ASCII value of the character). char c = 'A'; int ascii = (int) c; // ASCII value of 'A' System.out.println(ascii); // Output: 65 16. Int to Char (int to char) Convert an int (ASCII value) to a char. int ascii = 65; char c = (char) ascii; System.out.println(c); // Output: 'A' 17. Char to String (char to String) You can convert a char to a String using Character.toString() or String.valueOf(). char c = 'A'; String str = Character.toString(c); // Using Character.toString() String str2 = String.valueOf(c); // Using String.valueOf() System.out.println(str); // Output: "A" 18. String to Char (String to char) You can extract a single character from a String using charAt(). String str = "Hello"; char c = str.charAt(0); System.out.println(c); // Output: 'H' 19. Int to String (int to String) Using Concatenation You can also convert an int to a String by concatenating with an empty string. int num = 123; String str = num + ""; // Implicit conversion using concatenation System.out.println(str); // Output: "123" 20. String to Char Array (String to char[]) Convert a String to a char[] using toCharArray(). String str = "Hello"; char[] charArray = str.toCharArray(); System.out.println(Arrays.toString(charArray)); // Output: [H, e, l, l, o] 21. Char Array to String (char[] to String) Convert a char[] to a String using the String constructor. char[] charArray = {'H', 'e', 'l', 'l', 'o'}; String str = new String(charArray); System.out.println(str); // Output: "Hello"