ArrayList to Array Conversion in Java

ArrayList to Array Conversion in Java

Following methods can be used for converting ArrayList to Array

方法 1: 使用 public Object[] toArray() 方法

import java.util.ArrayList;
import java.util.List;

public class Test {
    public static void main(String[] args) {
        List<Integer> al = new ArrayList<Integer>();
        al.add(10);
        al.add(20);
        al.add(30);
        al.add(40);
        Object[] objects = al.toArray();
        for (Object obj : objects) {
            System.out.print(obj + " ");
        }
    }
}

运行结果

```
10 20 30 40
```

方法 2: 使用 public T[] toArray(T[] a) 方法

import java.util.ArrayList;
import java.util.List;

public class Test {
    public static void main(String[] args) {
        List<Integer> al = new ArrayList<Integer>();
        al.add(10);
        al.add(20);
        al.add(30);
        al.add(40);
        Integer[] arr = new Integer[al.size()];
        arr = al.toArray(arr);
        for (Integer x : arr) {
            System.out.print(x + " ");
        }
    }
}

运行结果

```
10 20 30 40
```

方法 3: 使用 public E get(int index) 方法

import java.util.ArrayList;
import java.util.List;

public class Test {
    public static void main(String[] args) {
        List<Integer> al = new ArrayList<Integer>();
        al.add(10);
        al.add(20);
        al.add(30);
        al.add(40);
        Integer[] arr = new Integer[al.size()];
        for (int i = 0; i < al.size(); i++) {
            arr[i] = al.get(i);
        }
        for (Integer x : arr) {
            System.out.print(x + " ");
        }
    }
}

运行结果

```
10 20 30 40
```

参考资料

• https://www.geeksforgeeks.org/arraylist-array-conversion-java-toarray-methods/