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();

}

}