List set to array

Hello everyone , I meet you again , I'm your friend, Quan Jun .

In the collection and array of small problems with each other

One 、 When a collection is converted to an array , Collection provides two methods

1,toArray , but its return value type is Object

During the strong turn, it will report java.lang.ClassCastException Class conversion exception

2,toArray The method with parameters of , When creating an array, specify the length of the array , Best with set size bring into correspondence with , Otherwise, the set length is greater than the array length , The original array Jiangbei is reset to null

Pictured , Specify the array length as the collection length

Pictured , The specified array length is less than the collection length

Two 、 Array to set

Use ： Arrays.asList( Array );

asList Back to a Array The inner class of , It has no way of the implementing collections , An error will occur when adding, deleting, and querying the returned set

Pictured ：

a1[0] = “toto”;// Modifying the original array will affect the converted set

Publisher ： Full stack programmer stack length , Reprint please indicate the source ：https://javaforall.cn/150684.html Link to the original text ：https://javaforall.cn