List<String> list = new ArrayList<>();
list.add("張三");
list.add("李四");
String[] strings1 = (String[]) list.toArray();//會報錯 java.lang.ClassCastException: java.lang.Object[] cannot be cast to java.lang.String[]
String[] stirngs2 = list.toArray(new String[0]);//最佳解決方式

依據：

public class ArrayList<E>....｛
.....
     public <T> T[] toArray(T[] var1) {
        if(var1.length < this.size) {
            return (Object[])Arrays.copyOf(this.elementData, this.size, var1.getClass());//轉換成var1所指的型別
        } else {
            System.arraycopy(this.elementData, 0, var1, 0, this.size);
            if(var1.length > this.size) {
                var1[this.size] = null;
            }

            return var1;
        }
    }
.......
｝