隐式类型转换不应该从char转换为String。(implicit type casting should not works from char to String. How is this pos

隐式类型转换不应该从char转换为String。(implicit type casting should not works from char to String. How is this possible ?)

从char转换为String应该会导致以下错误：此代码：

char [] arr = {'H', 'e', 'l', 'l', 'o'}; String c = arr[1];

错误：类型不匹配：无法从char转换为String

此代码：

char [] arr = {'H', 'e', 'l', 'l', 'o'}; String c = ""; for(char i : arr) { c += i; }

作品。

Converting from char to String should cause the following error: This code:

char [] arr = {'H', 'e', 'l', 'l', 'o'}; String c = arr[1];

Error :Type mismatch: cannot convert from char to String

This code :

char [] arr = {'H', 'e', 'l', 'l', 'o'}; String c = ""; for(char i : arr) { c += i; }

Works.

最满意答案

+=运算符，如+运算符，将执行字符串转换 ，其中一个操作数是一个String ，另一个不是。

+=的代码将使用字符串转换将i从char转换为String以便连接到c ，一个String 。

根据JLS的第5.2节 ，带=的代码不会使用字符串转换，因为它不在可分配上下文的可接受转换列表中。

The += operator, like the + operator, will perform string conversion, when one of its operands is a String and the other isn't.

The code with += will use string conversion to convert i from a char to a String for concatenation to c, a String.

The code with = will not use string conversion, because it's not in the list of acceptable conversions for assignment contexts, according to the JLS, Section 5.2.