Strings.java

import java.util.Scanner;

public class Strings {

    public static void printLetters(String str) {
        for (int i = 0; i < str.length(); i++) {
            System.out.print(str.charAt(i) + " ");
        }
        System.out.println();
    }

    public static boolean isPalindrome(String str) {
        for (int i = 0; i < str.length() / 2; i++) {
            if (str.charAt(i) != str.charAt(str.length() - 1 - i)) {
                return false;
            }
        }
        return true;
    }

    public static float Distance(String str) {
        int x = 0, y = 0;
        for (int i = 0; i < str.length(); i++) {
            switch (str.charAt(i)) {
                case 'N': // north
                    y++;
                    break;
                case 'E': // east
                    x++;
                    break;
                case 'W': // west
                    x--;
                    break;
                case 'S': // south
                    y--;
                    break;
            }
        }
        int x2 = x * x;
        int y2 = y * y;
        return (float) Math.sqrt(x2 + y2);
    }

    public static String toUpperCase(String str) {
        StringBuilder sb = new StringBuilder("");

        char ch = Character.toUpperCase(str.charAt(0));
        sb.append(ch);

        for (int i = 1; i < str.length(); i++) {
            if (str.charAt(i) == ' ') {
                sb.append(str.charAt(i));
                i++;
                sb.append(Character.toUpperCase(str.charAt(i)));
            } else {
                sb.append(str.charAt(i));
            }
        }
        return sb.toString();
    }

    public static String compress(String str) { // aaabbcccdd
        String newStr = "";
        for (int i = 0; i < str.length(); i++) {
            Integer count = 1;
            while (i < str.length() - 1 && str.charAt(i) == str.charAt(i + 1)) {
                count++;
                i++;
            }
            newStr += str.charAt(i);
            if (count > 1) {
                newStr += count.toString();
            }
        }
        return newStr;
    }

    public static String compress2(String str) { // aaabbcccdd
        StringBuilder newStr = new StringBuilder("");
        for (int i = 0; i < str.length(); i++) {
            Integer count = 1;
            while (i < str.length() - 1 && str.charAt(i) == str.charAt(i + 1)) {
                count++;
                i++;
            }
            newStr.append(str.charAt(i));
            if (count > 1) {
                newStr.append(count.toString());
            }
        }
        return newStr.toString();
    }

    public static void main(String args[]) {
        char arr[] = { 'a', 'b', 'c', 'd' };
        // defining string
        String str = "Aditya";
        String str2 = new String("Srivastava");

        Scanner sc = new Scanner(System.in);
        String name;
        // entire line as input
        name = sc.nextLine();
        System.out.print("Size of " + name + " is ");

        // length
        System.out.println(name.length());
        sc.close();

        // concatenation
        String FullName = str + " " + str2;
        System.out.println(FullName);
        printLetters(FullName);

        System.out.println(isPalindrome(name));
        String Distance = "WNEENESENNN";
        System.out.println(Distance(Distance));

        // .equals()
        System.out.println("************** .equals() function **************");
        String str3 = "Tony";
        String str4 = "Tony";
        String str5 = new String("Tony");

        if (str3 == str4) {
            System.out.println("Equal");
        } else {
            System.out.println("Not Equal");
        }
        if (str3 == str5) {
            System.out.println("Equal");
        } else {
            System.out.println("Not Equal");
        }
        if (str3.equals(str5)) {
            System.out.println("Equal");
        } else {
            System.out.println("Not Equal");
        }

        String fruits[] = { "apple", "mango", "banana" };

        String largest = fruits[0];
        for (int i = 1; i < fruits.length; i++) {
            if (largest.compareTo(fruits[i]) < 0) {
                largest = fruits[i];
            }
        }
        System.out.println(largest);

        StringBuilder sb = new StringBuilder("");
        for (char ch = 'a'; ch <= 'z'; ch++) { // time complexity = O(26)
            sb.append(ch);
        }
        System.out.println(sb);

        String str6 = "hi, i am aditya";
        System.out.println(toUpperCase(str6));

        String str7 = "aaabbcccdd";
        System.out.println(compress2(str7));
    }
}