Java II String Methods

length() String Method in Java, concat() String Method in Java, String Method equals() in Java, indexOf() String Method in Java, charAt() String Method in Java, toUpperCase() and toLowerCase() String Methods

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 Strings.

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!"