Strings in Java || Java + DSA course || Blog 6

Strings are defined as an array of characters. "Hello" is a string and "I am a student" is also a string.Strings are used in programming for various purpose.Strings are immutable, meaning it cannot be changed.To change it we use string builder.

Lets learn about strings in a practical way.

Declaration

String name = "Elon";

 

String lastname = "Musk";

 

String fullname = "Elon Musk";

 You can even make them print together like:

System.out.println(name + " " + lastname);

Output: Elon Musk

This is contatention/joining two strings. 

You can directly print it or save it in another variable as 

String fullname = name + lastname;

Length is the total space it has captured. The length of elon musk would be 9.

If you want to print the sentence letter by letter then charAt() function is used with for loop.

 compareTo() is used to see whether name1 and name2 strings are same. 

public class Main{

public static void main(String args[]){

String name1 = "Elon";

String name2 = "Elon";

if(name1.compareTo(name2) == 0){

System.out.println("YES");

}

}

}

 

The output will be YES.

Lets understand how it works:it works on alphabetical order. Lets take one string as "Bill" and another string as "Jeff". When we compare it b becomes before than j. so string1 is before than string 2. simply: string1 > string2. It returns a positive value like 8,1,4,3,...so it is not equal to 0 and it will not print YES.eg: hello<wello

Same if string1 was "jeff" and string2 was "bill", it would written negative value again not equal to zero.eg: hello>cello

But when elon and elon is seen, it returns zero and YES is printed.eg:hello==hello

Lets take a sentence

String sentence = "my name is Elon";

Java is a zero index based language. Indexing starts from zero.

 

What if we want to just print elon from the sentence. For this, we use.substring(index from which to start, index to end)

As i told you strings are immutable, so we use string builder

String Builder

normal string:

 stringbuilder

 

string doesnt take much time rather than string as it keeps changing itself.

Indexing

StringBuilder name = new StringBuilder("elon");

//indexing

System.out.println(name.charAt(0));

 

the output will be e.

SetCharAt()

StringBuilder name = new StringBuilder("elon");

//setCharAt

name.setCharAt(0,'u');

System.out.print(name);

 the output is ulon

.insert()

StringBuilder name = new StringBuilder("elon");

//insert

name.insert(0,'m');

System.out.print(name);

 the output is melon.

.delete()

StringBuilder name = new StringBuilder("elon");

//delete

name.delete(0,1);

System.out.print(name);

 the output is lon

.append()

StringBuilder name = new StringBuilder("elon");

//append

name.append("a");

System.out.print(name);

 the output is elona.

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