import java.util.*;

public class TestString {

	private static void stringDemo() {
		System.out.println("String demo");
		String palindrome = "Dot saw I was Tod";
        int len = palindrome.length();
        char[] tempCharArray = new char[len];
        char[] charArray = new char[len];
        
        System.out.println("Original palindrome: ");
        System.out.println(palindrome);
        System.out.println("Length = " + len);
        // put original string in an 
        // array of chars
        System.out.print("Characters in palindrome :");
        for (int i = 0; i < len; i++) {
            tempCharArray[i] = palindrome.charAt(i);
            System.out.print(tempCharArray[i] + " ");
        } 
        System.out.println("");

        // reverse array of chars
        for (int j = 0; j < len; j++) {
            charArray[j] = tempCharArray[len - 1 - j];
        }
        
        String reversePalindrome =
            new String(charArray); //Wrapping a deep copy of the original charArray
        System.out.println(reversePalindrome);
	}

	private static void stringBuilderDemo() {
		System.out.println("String builder demo");
		String palindrome = "Dot saw I was Tod";
        StringBuilder sb = new StringBuilder(palindrome);
        sb.reverse();  // reverse it
        System.out.println(sb);
        String reversed = sb.toString();

        // The same as above, since println(sb) implicitly calls sb.toString()
        System.out.println(reversed); 

        String[] strs = {"I ", "Love ", "Java"};
        StringBuilder sb2 = new StringBuilder();
        for (String str : strs) {
        	sb2.append(str);
        }
        String result = sb2.toString();
        System.out.println(result);

        sb2.setCharAt(2, 'l');
        sb2.setCharAt(7, 'j');
        System.out.println(sb2);
	}

	// StringBuilder is essentially a wrapper of char[],
	// with some additional funtionalities including resizing the char array.
	// If char array can do the job then we should just use char array
	private static void modifyString(String str) {
		char[] chars = str.toCharArray(); //Returns a deep copy of the char array in the string
		for (char c : chars) {
			System.out.print(c);
		}
		System.out.println("");
		for (int i = 0; i < chars.length; ++i) {
			if (i % 2 == 0) {
				chars[i] = '#';
			}
		}
		String modified = String.valueOf(chars); //Create a new string with a deep copy of chars array
                                                 //Essentially calls new String(chars)

		System.out.println("Modified: " + modified);
	}

    private static void testOtherMethods() {
        String str1 = "allen chin is a hero";
        int pos1 = str1.indexOf('a');
        //Should be 0
        System.out.println("Index of a in " + str1 + " after 0 is " + pos1);

        int pos2 = str1.indexOf('a', 3);
        //Should be 14
        System.out.println("Index of a in " + str1 + " after 3 is " + pos2);

        int pos3 = str1.indexOf('z');
        //Should be -1
        System.out.println("Index of z in " + str1 + "  is " + pos3);
    }

    private static void testTrimming() {
        String str1 = " asdf ";
        String str2 = "f sdfs ";
        String str3 = " jj./asf/fd  ";
        System.out.println("str1.trim()=" + str1.trim() + '#');
        System.out.println("str2.trim()=" + str2.trim() + '#');
        System.out.println("str3.trim()=" + str3.trim() + '#');
    }

    private static void testSubstring() {
        String s = "allen";
        System.out.println("Testing substrings of " + s);
        System.out.println("0, 1: " + s.substring(0, 1));
        System.out.println("0, 0: " + s.substring(0, 0));
        System.out.println("4, : " + s.substring(4));
        System.out.println("4, 4: " + s.substring(4, 4));
        System.out.println("5, : " + s.substring(5));
    }

    private static void testParsing() {
        String s = "104"; //Throw error if there are blanks in the string
        System.out.println(Integer.parseInt(s));

        int i = -67;
        s = String.valueOf(i);
        System.out.println(s);
    }

    private static void testSplit() {
        System.out.println("Testing String.split()..");
        String[] strs = new String[] {
            "/home/allen/haha", 
            "/haha/dd/",
            "//asd/",
            "/ha",
            "/haha//",
            "/"
        };
        for (String str : strs) {
            String[] splitted = str.split("/");
            System.out.println("Original string = " + str);
            System.out.println("Splited = " + Arrays.toString(splitted));
            System.out.println("");
        }
    }

	public static void main(String[] args) {
		stringDemo();
		System.out.println("");
		stringBuilderDemo();
		modifyString("Allen Chin");
        testOtherMethods();
        testTrimming();
        testSubstring();
        testParsing();
        testSplit();
	}
}