Information regarding the code is mentioned in the comments written next to each line.

public static void main(String[] args) {
            int num1 = sc.nextInt();       //take int input
            double num2 = sc.nextDouble();    //take double input
            long num3 = sc.nextLong();      //take long input
            float num4 = sc.nextFloat();     //take float input
            sc.nextLine();      //next line will throw error if you don't use this line of code
            String str = sc.nextLine();      //take String input
    }

In your code, you declare getInput method will return an int by:

public int getInput()

Since the name should be a String, not an int, you need to adjust your method signature:

public String getInput() {   
    lastName = input.nextLine();    
    return lastName;    
}

The standard input stream usually never ends if you do not indicate that. How could your program know, that the user does not enter another line?

So you should only read the lines that you explicitely know will get entered, like that:

Scanner input = new Scanner(System.in);
String first = input.nextLine();
String second = input.nextLine();
input.close();
System.out.println(first);
System.out.println(second);

If you want to have a variable number of lines, you should go with your while loop, but the user must indicate the end of input, as Christian suggested. Like that:

Scanner input = new Scanner(System.in);
StringBuilder builder = new StringBuilder();
while (input.hasNext()) {
    builder.append(input.nextLine()).append(System.lineSeparator());
}
input.close();
System.out.println(builder.toString());

Running that will loop infinitely (seemingly). But when pressing CTRL-Z you will end the input and input.hasNext() will return false. (Note, that CTRL-Z works in Linux and Windows.)

EDIT as per Erwin Bolwidt's comment to Christian's answer:

If you are redirecting the standard input stream, so that it for example reads from a file, the EOF marker (end of file) will indicate the end of input to the scanner. So obviously no user interaction is involved and the program will nevertheless behave correctly.