String -(Programs 1-10)

100 Java String Programming Questions

1. Write a program to find the length of a string.

class StringLength {
    public static void main(String[] args) {
        String str = "Hello World";
        System.out.println("Length of string: " + str.length());
    }
}
    

2. Write a program to print each character of a string.

public class PrintCharacters {
    public static void main(String[] args) {
        String str = "Hello Java";
        for (int i = 0; i < str.length(); i++) {
            System.out.println(str.charAt(i));
        }
    }
}
    

3. Write a program to reverse a string.

public class ReverseString {
    public static void main(String[] args) {
        String str = "Hello";
        String reversed = new StringBuilder(str).reverse().toString();
        System.out.println("Reversed: " + reversed);
    }
}
    

4. Write a program to check a string is palindrome .

class PalindromeCheck {
    public static void main(String[] args) {
        String str="Mal  ay=alam";
        String s = "";
        for (int i = 0; i < str.length(); i++) {
            char ch = str.charAt(i);
            if (ch >= 'A' && ch <= 'Z') {
                ch = (char)(ch + 32); // convert uppercase to lowercase
            }
            if ((ch >= 'a' && ch <= 'z') || (ch >= '0' && ch <= '9')) {
                s += ch; 
            }
        }

        boolean isPalindrome = true;
        int left = 0, right = s.length() - 1;
        while (left < right) {
            if (s.charAt(left) != s.charAt(right)) {
                isPalindrome = false;
                break;
            }
            left++;
            right--;
        }

        if (isPalindrome) {
            System.out.println("Palindrome");
        } else {
            System.out.println("Not a Palindrome");
        }

    }
}

5. Count the number of Vowels in a String.

class VowelCount {
    public static void main(String[] args) {
        String str="maluyilom";
        int count = 0;
        for (int i = 0; i < str.length(); i++) {
            char ch = str.charAt(i);
            if (ch >= 'A' && ch <= 'Z') {
                ch = (char)(ch + 32);
            }
            if (ch == 'a' || ch == 'e' || ch == 'i' || ch == 'o' || ch == 'u') {
                count++;
            }
        }

        System.out.println("Number of vowels in "+str+" - " + count);
       }
}

6. Count the number of Consonants in a String.

class ConsonantCount {
    public static void main(String[] args) {
        String str="abcdefghi";
        int count = 0;
        for (int i = 0; i < str.length(); i++) {
            char ch = str.charAt(i);
            if (ch >= 'A' && ch <= 'Z') {
                ch = (char)(ch + 32);
            }
            if (ch >= 'a' && ch <= 'z') {
                if (!(ch == 'a' || ch == 'e' || ch == 'i' || ch == 'o' || ch == 'u')) {
                    count++;
                }
            }
        }
        System.out.println("Number of consonants: " + count);
    }
}
/*
class ConsonantCount {
    public static void main(String[] args) {
        String str = "abcdefghi".toLowerCase();
        int count = 0;

        for (int i = 0; i < str.length(); i++) {
            char ch = str.charAt(i);
            if (ch >= 'a' && ch <= 'z' && "aeiou".indexOf(ch) == -1) {
                count++;
            }
        }

        System.out.println("Number of consonants: " + count);
    }
}*/

7. Count the number of Digits in a String.

class CountDigits {
    public static void main(String[] args) {
        String str = "Hello123World456";
        int count = 0;

        for (int i = 0; i < str.length(); i++) {
            if (str.charAt(i) >= '0' && str.charAt(i) <= '9') {
                count++;
            }
        }
        System.out.println("Digits: " + count);
    }
}

8. Count the number of Spaces in a String.

class CountSpaces {
    public static void main(String[] args) {
        String str = "Hello World Java Program";
        int count = 0;

        for (int i = 0; i < str.length(); i++) {
            if (str.charAt(i) == ' ') {
                count++;
            }
        }
        System.out.println("Spaces: " + count);
    }
}

9. Count the number of Special Characters in a String.

class CountSpecialChars {
    public static void main(String[] args) {
        String str = "Hello@Java#2025!";
        int count = 0;
        for (int i = 0; i < str.length(); i++) {
            char ch = str.charAt(i);
            if (!(ch >= 'a' && ch <= 'z') && 
                !(ch >= 'A' && ch <= 'Z') && 
                !(ch >= '0' && ch <= '9') && 
                ch != ' ') {
                count++;
            }
        }
        System.out.println("Special Characters: " + count);
    }
}

10. Convert the string into Upper Case.

public class ToUpperCase {
    public static void main(String[] args) {
        String str = "first hello world java";
        String upper = "";

        for (int i = 0; i < str.length(); i++) {
            char ch = str.charAt(i);
            if (ch >= 'a' && ch <= 'z') {
                upper += (char)(ch - 32);
            } else {
                upper += ch;
            }
        }
        System.out.println("Uppercase: " + upper);
        String str1 = "second hello world java";
        String upper1=str1.toUpperCase();
        System.out.println("Uppercase: " + upper1);
        
    }
}