Explain java.lang.string library in java?
Strings are objects. Specifically they're instances of the class java.lang.String. This class has several methods which are useful for working along with strings.
Internally Java Strings are arrays of Unicode characters. For instance the String "Hello" is a five element array. Like arrays, Strings starts counting at 0. Therefore in the String "Hello" 'H' is character 0, 'e' is character 1, and so on.