Error adding to ArrayList - Java

Question

This is a snippet of my code:

import java.util.Scanner;
import java.util.ArrayList;
import java.util.Collections;
public class Spiral3{
 public static ArrayList<Integer> R = new ArrayList<Integer>(); 
 public static ArrayList<Integer> K = new ArrayList<Integer>();
 R.add(1);
 K.add(1);
 public static String pekare = "H";

All I'm trying to do here is create two arrays with the first element int 1. So R = [1], K = [1]. I get the following error:

Spiral3.java:8: error: <identifier> expected
 R.add(1);
 ^
Spiral3.java:8: error: illegal start of type
 R.add(1);
 ^
Spiral3.java:9: error: <identifier> expected
 K.add(1);
 ^
Spiral3.java:9: error: illegal start of type
 K.add(1);

What's going on here? Thankful for your help :)

Answer 1

R.add(1);
K.add(1);

These statements should be inside some method or constructor or initializer block.

For example :

static {
 R.add(1);
 K.add(1);
}

• Sahand: Could I possibly add them in the initialization to avoid having to add them inside a method?
• Eran: @user3128156 You can use a static initializer block (see my edit).

Answer 2

If you want the list to be initialized to those values, you can pass it as List:

public static ArrayList<Integer> R = new ArrayList<Integer>(Arrays.asList(1)); 
public static ArrayList<Integer> K = new ArrayList<Integer>(Arrays.asList(1));

Answer 3

You should do like this;

 // create an array list
 ArrayList al = new ArrayList();
 System.out.println("Initial size of al: " + al.size());
 // add elements to the array list
 al.add("C");
 al.add("A");
 al.add("E");