六个Java集合使用时需要注意的事项

String [] s= new String[]{
    "dog", "lazy", "a", "over", "jumps", "fox", "brown", "quick", "A"
};
List<String> list = Arrays.asList(s);
Collections.reverse(list);
//没有指定类型的话会报错
s=list.toArray(new String[0]);

String[] myArray = {"Apple", "Banana", "Orange"};
List<String> myList = Arrays.asList(myArray);
//上面两个语句等价于下面一条语句
List<String> myList = Arrays.asList("Apple","Banana", "Orange");

int[] myArray = {1, 2, 3};
List myList = Arrays.asList(myArray);
System.out.println(myList.size());// 1
System.out.println(myList.get(0));// 数组地址值
System.out.println(myList.get(1));// 报错：ArrayIndexOutOfBoundsException
int[] array = (int[]) myList.get(0);
System.out.println(array[0]);// 1

Integer[] myArray = {1, 2, 3};

List myList = Arrays.asList(1, 2, 3);
myList.add(4);// 运行时报错：UnsupportedOperationException
myList.remove(1);// 运行时报错：UnsupportedOperationException
myList.clear();// 运行时报错：UnsupportedOperationException

//jdk1.5+
static <T> List<T> arrayToList(final T[] array) {
  final List<T> l = new ArrayList<T>(array.length);

  for (final T s : array) {
    l.add(s);
  }
  return l;
}


Integer [] myArray = { 1, 2, 3 };
System.out.println(arrayToList(myArray).getClass()); // class java.util.ArrayList

List list = new ArrayList<>(Arrays.asList("a", "b", "c"))

Integer [] myArray = { 1, 2, 3 };
List myList = Arrays.stream(myArray).collect(Collectors.toList());
// 基本类型也可以实现转换（依赖boxed的装箱操作）
int [] myArray2 = { 1, 2, 3 };
List myList = Arrays.stream(myArray2).boxed().collect(Collectors.toList());

Integer[] array = {1, 2, 3};
List<Integer> list = List.of(array);