java 38 | String class methods | compareTo() method | toLowerCase() | string concat using + смотреть онлайн

String class has various methods, I am going to cover few of them.
At the end of this class students will be able to : -
Apply charAt ( ) method to find a character at particular place
Apply replace( ) method to replace one char with other
Apply compareTo( ) method to compare two strings.
Apply concat( ) method for concatenation of strings.

There are various methods available in string class
 concat(), equals(), split(), length(), replace(), compareTo(), intern(), substring() etc.
We are going to see some of the methods

int length(): Returns the number of characters in the String.
“welcome".length();  // returns 7
char charAt(int i): Returns the character at ith index. “welcome".charAt(3); // returns  ‘c’
String substring (int i): Return the substring from the ith  index character to end.
“welcomeStudents".substring(3); // returns “comeStudents”

 String replace (char oldChar, char newChar) :  Returns new string by replacing all occurrences of oldChar with newChar.
String s1 = “feeksforfeeks”;
String s2 = “feeksforfeeks”.replace(‘f’ ,’g’);
// returns “geeksgorgeeks”

int compareTo (String str2) : It compares values lexicographically and return an integer value that describes if first string is less than, greater than or equal to second string.
str1.compareTo(str2) :-
If str1 greaterThan str2 return 1
If str1lessThan str2 return -1
If str1==str2 return 0

boolean equals( Object otherObj): Compares this string to the specified object.
Boolean out = “Geeks”.equals(“Geeks”); // returns true Boolean out = “Geeks”.equals(“geeks”); // returns false

String toLowerCase(): Converts all the characters in the String to lower case.
String word1 = “HeLLo”;
String word3 = word1.toLowerCase(); // returns “hello"
String toUpperCase(): Converts all the characters in the String to upper case.
String word1 = “HeLLo”;
String word2 = word1.toUpperCase(); // returns “HELLO”

String concat( String str): Concatenates specified string to the end of this string.
String s1 = ”Welcome”;
String s2 = “Students”;
String output = s1.concat(s2);//returns “WelcomeStudents”
Other way of concatenation:
By using the “ + ” operator
String s= “welcome ” + “ Students”// welcomeStudents
Compiler will convert the above statement like this:-
String s = ( new StringBuilder( )).append(“welcome”) .append(“Students”).toString();
StringBuilder is a mutable class.
toString convert into string class
235+apartment : this will also work

summary
There are various methods in string class
We can make use of these methods in our program
To find some char at some location
To replace any character at any location
To append other string into the string
To change into upper case or lower case any string