JAVA中length、length()、size()的区别

import java.util.ArrayList;
import java.util.List;
public class Test {
public static void main(String[] args) {
String s = "abcd";
int[] a = new int[5];
List list = new ArrayList<>();
list.add(1);
list.add(2);
list.add(3);
System.out.println(s.length());
System.out.println(a.length);
System.out.println(list.size());
}
}