length() String Method in Java
In Java, the length()
string method returns the total number of characters – the length – of a String
.
String str = "Codecademy";
System.out.println(str.length());
// prints 10
concat() String Method in Java
In Java, the concat()
string method is used to append one String
to the end of another String
. This method returns a String
representing the text of the combined strings.
String s1 = "Hello";
String s2 = " World!";
String s3 = s1.concat(s2);
// concatenates strings s1 and s2
System.out.println(s3);
// prints "Hello World!"
String Method equals() in Java
In Java, the equals()
string method tests for equality between two String
s.
equals()
compares the contents of each String
. If all of the characters between the two match, the method returns true
. If any of the characters do not match, it returns false
.
Additionally, if you want to compare two strings without considering upper/lower cases, you can use .equalsIgnoreCase()
.
String s1 = "Hello";
String s2 = "World";
System.out.println(s1.equals("Hello"));
// prints true
System.out.println(s2.equals("Hello"));
// prints false
System.out.println(s2.equalsIgnoreCase("world"));
// prints true
indexOf() String Method in Java
In Java, the indexOf()
string method returns the first occurence of a character or a substring in a String
. The character/substring that you want to find the index of goes inside of the ()
.
If indexOf()
cannot find the character or substring, it will return -1.
String str = "Hello World!";
System.out.println(str.indexOf("l"));
// prints 2
System.out.println(str.indexOf("Wor"));
// prints 6
System.out.println(str.indexOf("z"));
// prints -1
charAt() String Method in Java
In Java, the charAt()
string method returns the character of a String
at a specified index. The index value is passed inside of the ()
, and should lie between 0 and length()-1
.
String str = "This is a string";
System.out.println(str.charAt(0));
// prints 'T'
System.out.println(str.charAt(15));
// prints 'g'
toUpperCase() and toLowerCase() String Methods
In Java, we can easily convert a String
to upper and lower case with the help of a few string methods:
toUpperCase()
returns the string value converted to uppercase.toLowerCase()
returns the string value converted to lowercase.
String str = "Hello World!";
String uppercase = str.toUpperCase();
// uppercase = "HELLO WORLD!"
String lowercase = str.toLowerCase();
// lowercase = "hello world!"