WLT-Java

Explanation:

Traverse the string character by character and add each character to the result only if it is not already present. This keeps the first occurrence and removes duplicates.

String str = "I am in Hyderabad";
str = str.toLowerCase();
String expected = "";

for (int i = 0; i < str.length(); i++)
{
    char ch = str.charAt(i);
    if (!expected.contains(ch + ""))
    {
        expected = expected + ch;
    }
}
System.out.print(expected);

Explanation:

Compare each character with the remaining characters in the string. If a match is found, treat it as a duplicate and store it only once.

String str = "I am in Hyderabad";
str = str.toLowerCase();
String expected = "";

for (int i = 0; i < str.length(); i++)
{
    char ch = str.charAt(i);
    for (int j = i + 1; j < str.length(); j++)
    {
        char ch1 = str.charAt(j);
        if (ch == ch1)
        {
            if (!expected.contains(ch + ""))
            {
                expected = expected.concat(ch + "");
            }
        }
    }
}
System.out.print(expected);

Explanation:

First extract unique characters, then count how many times each one appears in the original string.

String str = "I am in Hyderabad";
str = str.toLowerCase();
String expected = "";

for (int i = 0; i < str.length(); i++)
{
    char ch = str.charAt(i);
    if (!expected.contains(ch + ""))
    {
        expected = expected + ch;
    }
}

for (int i = 0; i < expected.length(); i++)
{
    char x = expected.charAt(i);
    int c = 0;

    for (int j = 0; j < str.length(); j++)
    {
        if (x == str.charAt(j))
        {
            c++;
        }
    }
    System.out.println(x + " came " + c + " times");
}

Explanation:

Count occurrences of each unique character and print only those whose count is greater than one.

String str = "I am in Hyderabad";
str = str.toLowerCase();
String expected = "";

for (int i = 0; i < str.length(); i++)
{
    char ch = str.charAt(i);
    if (!expected.contains(ch + ""))
    {
        expected = expected + ch;
    }
}

for (int i = 0; i < expected.length(); i++)
{
    char x = expected.charAt(i);
    int c = 0;

    for (int j = 0; j < str.length(); j++)
    {
        if (x == str.charAt(j))
        {
            c++;
        }
    }
    if (c > 1)
    {
        System.out.println(x + " came " + c + " times");
    }
}

Explanation:

Store character frequencies in a HashMap, find the maximum value, and print all characters having that maximum count.

String str = "javav1234 java324 is good434";
char[] ch = str.toCharArray();

HashMap<Character, Integer> hm = new HashMap<>();

for (int i = 0; i < ch.length; i++)
{
    if (hm.containsKey(ch[i]))
    {
        hm.put(ch[i], hm.get(ch[i]) + 1);
    }
    else
    {
        hm.put(ch[i], 1);
    }
}

int max = 0;
for (char c : hm.keySet())
{
    if (hm.get(c) > max)
    {
        max = hm.get(c);
    }
}

List<Character> maxv = new ArrayList<>();
for (char c : hm.keySet())
{
    if (hm.get(c) == max)
    {
        maxv.add(c);
    }
}

System.out.println("Max Characters " + maxv + " value is " + max);

Explanation:

Traverse each character and use Character utility methods to classify and count occurrences.

String str = "2543%#$@$fsdfdsafadsfdasf khlkj ##!#!@ DFAS DSAF";
char[] ch = str.toCharArray();

HashMap<Character, Integer> hm = new HashMap<>();

for (int i = 0; i < ch.length; i++)
{
    if (!Character.isLetterOrDigit(ch[i]))
    {
        if (!hm.containsKey(ch[i]))
        {
            hm.put(ch[i], 1);
        }
        else
        {
            hm.put(ch[i], hm.get(ch[i]) + 1);
        }
    }
}
System.out.println(hm);

Explanation:

Extract digits using modulo and division and store their frequency using a HashMap.

int num = 3214312;
int temp = num;

HashMap<Integer, Integer> hm = new HashMap<>();

while (temp != 0)
{
    int d = temp % 10;
    if (hm.containsKey(d))
    {
        hm.put(d, hm.get(d) + 1);
    }
    else
    {
        hm.put(d, 1);
    }
    temp = temp / 10;
}
System.out.print(hm);

Explanation:

Reverse the string, remove spaces, then rebuild the output by inserting spaces at original positions.

String original = "hi cat book";
String reverse = "";

for (int i = original.length() - 1; i >= 0; i--)
{
    reverse = reverse + original.charAt(i);
}

reverse = reverse.replaceAll(" ", "");

String output = "";
int j = 0;

for (int i = 0; i < original.length(); i++)
{
    if (original.charAt(i) == ' ')
    {
        output = output + ' ';
    }
    else
    {
        output = output + reverse.charAt(j++);
    }
}
System.out.print(output);

Explanation:

Traverse each character and consider only alphabetic characters that are not vowels. Store each consonant in a HashMap and update its count.

String str = "javav1234 java324 is good434 $@!$#$#@!";
char ch[] = str.toCharArray();
HashMap<Character, Integer> hm = new HashMap<>();

for (int i = 0; i < ch.length; i++)
{
    if (Character.isLetter(ch[i]) &&
        !(ch[i]=='a'||ch[i]=='e'||ch[i]=='i'||ch[i]=='o'||ch[i]=='u'))
    {
        if (hm.containsKey(ch[i]))
        {
            hm.put(ch[i], hm.get(ch[i]) + 1);
        }
        else
        {
            hm.put(ch[i], 1);
        }
    }
}
System.out.print(hm);

Explanation:

Split the string into words and print only those words that do not contain any vowels.

String str = "SKY fly my JAVA color";
String words[] = str.split(" ");

for (String word : words)
{
    if (!word.contains("a") && !word.contains("e") &&
        !word.contains("i") && !word.contains("o") &&
        !word.contains("u") && !word.contains("A") &&
        !word.contains("E") && !word.contains("I") &&
        !word.contains("O") && !word.contains("U"))
    {
        System.out.print(word + " ");
    }
}

// Alternative using regex
String str = "SKY fly my JAVA color";
String words[] = str.split(" ");

for (String word : words)
{
    if (!word.toLowerCase().matches(".*[aeiou].*"))
    {
        System.out.print(word + " ");
    }
}

Explanation:

Split the string into words and print only those words that do not contain any vowels.

String str = "SKY fly my JAVA color";
String words[] = str.split(" ");

for (String word : words)
{
    if (!word.contains("a") && !word.contains("e") &&
        !word.contains("i") && !word.contains("o") &&
        !word.contains("u") && !word.contains("A") &&
        !word.contains("E") && !word.contains("I") &&
        !word.contains("O") && !word.contains("U"))
    {
        System.out.print(word + " ");
    }
}

// Alternative using regex
String str = "SKY fly my JAVA color";
String words[] = str.split(" ");

for (String word : words)
{
    if (!word.toLowerCase().matches(".*[aeiou].*"))
    {
        System.out.print(word + " ");
    }
}

Explanation:

Extract digits and text separately from each word, convert the digits to a number, and print the text that many times.

String str = "12cars 17bicycles 21lorries 9a";
String words[] = str.split(" ");

for (String word : words)
{
    String numbers = "";
    String text = "";

    for (int i = 0; i < word.length(); i++)
    {
        char ch = word.charAt(i);
        if (Character.isDigit(ch))
        {
            numbers = numbers + ch;
        }
        else
        {
            text = text + ch;
        }
    }

    int number = Integer.parseInt(numbers);
    for (int i = 0; i < number; i++)
    {
        System.out.print(text + " ");
    }
    System.out.println();
}

Explanation:

First copy all zeros into a new array, then copy non-zero elements while preserving order.

int input[] = {3,4,0,5,6,0,9};
int output[] = new int[input.length];
int j = 0;

for (int i = 0; i < input.length; i++)
{
    if (input[i] == 0)
    {
        output[j++] = 0;
    }
}

for (int i = 0; i < input.length; i++)
{
    if (input[i] != 0)
    {
        output[j++] = input[i];
    }
}

for (int k = 0; k < output.length; k++)
{
    System.out.print(output[k]);
}

Explanation:

Copy non-zero elements first, followed by zeros, while maintaining order.

int input[] = {3,4,0,5,6,0,9};
int output[] = new int[input.length];
int j = 0;

for (int i = 0; i < input.length; i++)
{
    if (input[i] != 0)
    {
        output[j++] = input[i];
    }
}

for (int i = 0; i < input.length; i++)
{
    if (input[i] == 0)
    {
        output[j++] = 0;
    }
}

for (int k = 0; k < output.length; k++)
{
    System.out.print(output[k]);
}

Explanation:

Ignore words without digits and display text only for words containing numbers.

String str = "cars 17bicycles lorries 9a";
String words[] = str.split(" ");

for (String word : words)
{
    String numbers = "";
    String text = "";

    for (int i = 0; i < word.length(); i++)
    {
        char ch = word.charAt(i);
        if (Character.isDigit(ch))
        {
            numbers = numbers + ch;
        }
        else
        {
            text = text + ch;
        }
    }

    if (numbers.isEmpty())
    {
        continue;
    }

    int number = Integer.parseInt(numbers);
    for (int i = 0; i < number; i++)
    {
        System.out.print(text + " ");
    }
    System.out.println();
}

Explanation:

If a word does not contain a number, default it to zero to avoid errors.

String str = "cars 17bicycles lorries 9a";
String words[] = str.split(" ");

for (String word : words)
{
    String numbers = "";
    String text = "";

    for (int i = 0; i < word.length(); i++)
    {
        char ch = word.charAt(i);
        if (Character.isDigit(ch))
        {
            numbers = numbers + ch;
        }
        else
        {
            text = text + ch;
        }
    }

    if (numbers.isEmpty())
    {
        numbers = numbers + 0;
    }

    int number = Integer.parseInt(numbers);
    for (int i = 0; i < number; i++)
    {
        System.out.print(text + " ");
    }

    System.out.println();
    System.out.println(numbers + " " + text + " displayed");
}

Explanation:

Print each word as many times as its length.

String str = "hi cat book";
String words[] = str.split(" ");

for (String word : words)
{
    int length = word.length();
    for (int i = 0; i < length; i++)
    {
        System.out.print(word + " ");
    }
    System.out.println();
    System.out.println(word + " is displayed " + length + " times.");
}

Explanation:

Reverse the string, remove spaces, and rebuild the output while keeping spaces at original positions.

String original = "hi cat book";
String reverse = "";

for (int i = original.length() - 1; i >= 0; i--)
{
    reverse = reverse + original.charAt(i);
}

reverse = reverse.replaceAll(" ", "");

String output = "";
int j = 0;

for (int i = 0; i < original.length(); i++)
{
    if (original.charAt(i) == ' ')
    {
        output = output + ' ';
    }
    else
    {
        output = output + reverse.charAt(j++);
    }
}
System.out.print(output);

Explanation:

Preserve vowels and spaces at original positions while reversing the remaining characters.

String original = "hi cat book";
String reverse = "";

for (int i = original.length() - 1; i >= 0; i--)
{
    reverse = reverse + original.charAt(i);
}

for (int i = 0; i < reverse.length(); i++)
{
    if (reverse.charAt(i)=='a'||reverse.charAt(i)=='e'||
        reverse.charAt(i)=='i'||reverse.charAt(i)=='o'||
        reverse.charAt(i)=='u'||reverse.charAt(i)=='A'||
        reverse.charAt(i)=='E'||reverse.charAt(i)=='I'||
        reverse.charAt(i)=='O'||reverse.charAt(i)=='U'||
        reverse.charAt(i)==' ')
    {
        reverse = reverse.replace(reverse.charAt(i) + "", "");
    }
}

String output = "";
int j = 0;

for (int i = 0; i < original.length(); i++)
{
    if (original.charAt(i)=='a'||original.charAt(i)=='e'||
        original.charAt(i)=='i'||original.charAt(i)=='o'||
        original.charAt(i)=='u'||original.charAt(i)=='A'||
        original.charAt(i)=='E'||original.charAt(i)=='I'||
        original.charAt(i)=='O'||original.charAt(i)=='U'||
        original.charAt(i)==' ')
    {
        output = output + original.charAt(i);
    }
    else
    {
        output = output + reverse.charAt(j++);
    }
}

System.out.println(output);

Explanation:

Preserve uppercase letters and spaces at their original positions while reversing the remaining characters.

String original = "JAVA is GOOD programming LANguage";
String reverse = "";

for (int i = original.length() - 1; i >= 0; i--)
{
    reverse = reverse + original.charAt(i);
}

for (int i = 0; i < reverse.length(); i++)
{
    if ((reverse.charAt(i) >= 'A' && reverse.charAt(i) <= 'Z')
        || reverse.charAt(i) == ' ')
    {
        reverse = reverse.replace(reverse.charAt(i) + "", "");
    }
}

String output = "";
int j = 0;

for (int i = 0; i < original.length(); i++)
{
    if ((original.charAt(i) >= 'A' && original.charAt(i) <= 'Z')
        || original.charAt(i) == ' ')
    {
        output = output + original.charAt(i);
    }
    else
    {
        output = output + reverse.charAt(j++);
    }
}

System.out.println(output);

WLT-Java Problems and Solutions