How to use import java.lang

Question

My code..
import java.util.Scanner;
import java.lang.*;
//import java.io.*;I
public class BankTransaction {

public static void main (String args[]) ) {
//TODO code application logic here
Scanner var=new(System.in);

int pin;
double initial, amount, sum, difference;
initial = 5000.00;
System.out.println ("Enter your pin:");
pin=var. nextInt (); {
Doesn't seem to work and always turn into like this..
java.lang.ClassNotFoundException: Didn't find class "null.BankTransaction" on path: DexPathList[[dex file "/storage/emulated/0/JavaNIDE/PrestonBank/app/build/dexedClasses/classes.dex"],nativeLibraryDirectories=[/vendor/lib, /system/lib]]
at dalvik.system.BaseDexClassLoader.findClass(BaseDexClassLoader.java:56)...

...every time i run it

Answer 1

you dont need to import java.lang its there by default

Answer 2

because its the java core. System, String, data type wrapper, Thread, Exception, Error.
almost everything is in there,

Answer 3

Thanks, but how did it become default?