String - najczęściej używane metody

Substring

• public String substring(int startIndex) 
• public String substring(int startIndex, int endIndex)

String s= "Hello World";
System.out.println(s.substring(3));
System.out.println(s.substring(1,3));

StringBuffer - creates mutable string. String is originally immutable. Used operation on Strings

        StringBuffer buffer = new StringBuffer("Hello World");
        buffer.append(" GREAT ADDITION");
        System.out.println(buffer);

StringBuilder - more efficient than StringBuffor
https://www.javatpoint.com/StringBuilder-class

• charAt() - returns char on defined index
• contains() - true false
• endsWith()  startsWith() - 
• indexOf() - returns index of char
• isEmpty() - true false
• length() - 
• replace() - replace char 
• split()
• trim() - 
• toLowerCase() i toUpperCase

String format() - method returns the formatted string by given locale, format and arguments