```
// "static void main" must be defined in a public class.
public class Main {
public static void main(String[] args) {
// 1. initialize
List<Integer> v0 = new ArrayList<>();
List<Integer> v1; // v1 == null
// 2. 将普通数组变为动态数组
Integer[] a = {0, 1, 2, 3, 4};
v1 = new ArrayList<>(Arrays.asList(a));
// 3. make a copy
List<Integer> v2 = v1; // another reference to v1
List<Integer> v3 = new ArrayList<>(v1); // make an actual copy of v1
// 3. get length
System.out.println("The size of v1 is: " + v1.size());;
// 4. access element
System.out.println("The first element in v1 is: " + v1.get(0));
// 5. iterate the vector
System.out.print("[Version 1] The contents of v1 are:");
for (int i = 0; i < v1.size(); ++i) {
System.out.print(" " + v1.get(i));
}
System.out.println();
System.out.print("[Version 2] The contents of v1 are:");
for (int item : v1) {
System.out.print(" " + item);
}
System.out.println();
// 6. modify element
v2.set(0, 5); // modify v2 will actually modify v1
System.out.println("The first element in v1 is: " + v1.get(0));
v3.set(0, -1);
System.out.println("The first element in v1 is: " + v1.get(0));
// 7. sort
Collections.sort(v1);
// 8. add new element at the end of the vector
v1.add(-1);
v1.add(1, 6);
// 9. delete the last element
v1.remove(v1.size() - 1);
}
}
```
