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 10concat() 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 -1charAt() 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!"