Structure of the String class

"What do you think, Amigo? What is the most popular Java class after int?"

"You already gave me a spoiler in the title of the lesson, Ellie. It's String!"

"Indeed, it is a spoiler. String is used absolutely everywhere. It has a bunch of useful methods that you are better off knowing.

"The String class is the only class other than primitive types whose literals can be used in a switch statement; the compiler handles string addition and String objects in a special way; String objects are storied in memory in a special way. Basically, the String class is a very special class.

"Also, the Stringclass has a bunch of helper classes whose purpose is to further simplify working with strings in Java. When you learn all this, many thing will really become much easier for you to do."

"I can't wait."

"Well, we'll start from the very core of this ecosystem — the organization of the String class. The structure of the String class is actually very simple: inside it is a character array (char array) that stores all the characters of the string. For example, this is how the word 'Hello' is stored:

It's important.

Actually, this is not quite accurate. Because the String class is very important, it uses a lot of optimizations, and the data is internally stored not as a character array, but simply as a byte array.

Methods of the String class

The String class has a lot of methods: it has 18 constructors alone! So, below I will list only the most frequently used ones:

int length()

boolean isEmpty()

boolean isBlank()

char charAt(int index)

char[] toCharArray()

byte[] getBytes()

String[] split(String regex)

String join(CharSequence delimiter, elements)

String intern()

"That looks very good!"

"Let's write a program that converts a file path from Unix style to Windows style. Unix uses the / character to separate folders, while Windows uses the \ character.

Solution 1. Using a char array

Scanner console = new Scanner(System.in);
String path = console.nextLine();

char[] chars = path.toCharArray();
for (int i = 0; i < chars.length; i++)
   if (chars[i] == '/')
      chars[i] = '\\';

String result = new String(chars);
System.out.println(result);

Solution 2. Using the split() and join() methods:

Scanner console = new Scanner(System.in);
String path = console.nextLine();

String array[] = path.split("\\/");


String result = String.join("\\", array);


System.out.println(result);

Solution 3. Using the replace(char oldChar, char newChar) method:

Scanner console = new Scanner(System.in);
String path = console.nextLine();

String result = path.replace('/', '\\');

System.out.println(result);

"I liked the third solution the most. But I'll practice all three."

"Well done, Amigo. I see that you're already impatient to put your new knowledge into practice. The lesson is over."