DEV Community: Souravsing Pardeshi

3.Stringbuilder class in java

Souravsing Pardeshi — Mon, 21 Feb 2022 08:11:18 +0000

Java Stringbuilder class

Strings in java are immutable (not editable)
so to make changes in string we use this string builder class which makes the string mutable (editable)
there are different methods which comes with stringbuilder class as shown below

1.Append:

This method will simply append an string to existing string.

2.Insert:

this will insert an character or strig at given position in given string.

3.Replace:

this will replace certain part of string with another string.
it take position of string which need to be replaced.

4.Delete:

this method will delete certain part of string by taking starting and ending position.

2. Basic String operations

Souravsing Pardeshi — Mon, 21 Feb 2022 07:27:35 +0000

Declaring string and assigning value to it

public class main{
    public static void main(String[] args){
        String str1 = " hello world";
        System.out.println(str1);
    }
}

Concatination of strings

public class main{
    public static void main(String[] args){
        String str1 = " hello world";
        String str2 = "India";
        String str3 = str1+str2;
        System.out.println(str3);
    }
}

Accessing element from its position

public class main{
    public static void main(String[] args){
        String str1 = " hello world";
        //charAt(pos) is used to access element in string at pos position.
        System.out.println(str1.charAt(2));
    }
}

Getting substring from string

public class main{
    public static void main(String[] args){
        String str1 = " hello world";
        //substring get substring from a string by accepting starting and ending position.
        System.out.println(str1.substring(2,4));
    }
}

Using split method

public class main{
    public static void main(String[] args){
        String str1 = "A,B,C,D";
        String str2 = "H I J k";
        //will split string by using , as identifier
        String [] arr1 = str1.split(",");
        // will split string by using space as identifier
        String [] arr2 = str2.split(" ");
    }
}

String inbuilt methods

public class main{
    public static void main(String[] args){
        String str1 = " hello world";
        // will return length of string
        System.out.println(str1.length());
        // will convert all char to uppercase
        System.out.println(str1.toUpperCase());
        //check if string starts with "h"
        System.out.println(str1.startsWith("h"));
        //check if string ends with "h"
        System.out.println(str1.endsWith("h"));
        //will find index of "ll"
        System.out.println(str1.indexOf("ll"));
        // will return index of last occurence if "hello"
        System.out.println(str1.lastIndexOf("hello"));
        //will replace hello with bye
        System.out.println(str1.replace("hello", "bye"));
        System.out.println(str1);
        System.out.println(Integer.toBinaryString(a));
        System.out.println(Integer.toHexString(a));
        System.out.println(Integer.parseInt(Integer.toString(a)));
    }
}

1.Main Method in java

Souravsing Pardeshi — Mon, 21 Feb 2022 07:05:49 +0000

public class main{
    public static void main(String[] args)
    {
        //code
    }
}

entry level is main method.
this method is public so it can be easily found by jvm.
void because not expected to return anything.
static so no need to create object of class for execution.
String[] args are array of string as arguments for code.