为什么在System.out.println（）中不增加字符？

问题描述

  
 
 
但是， char1 + =  1; 或 char1 ++ 不执行二进制数字促销，因此可按预期工作。
 
 
 
引用：
（强调我）
 
char char1 = 'a';
System.out.println(char1);      //prints char 1
System.out.println(char1+1);    //prints char 1
System.out.println(char1++);     //prints char 1
System.out.println(char1+=1);    //prints incremented char1
char1 += 1;
System.out.println(char1);      //prints incremented char1
In the above, why doesn't (char1+1) or (char++) print the incremented character but theother two do?
 解决方案 
First, I'm assuming that because you say the increment in System.out.println works, that you have really specified:
char char1 = 'a';
EDIT
In response to the change of the question (char1+1; => char1 += 1;) I see the issue.The output is
a
98
b
The 98 shows up because the char a was promoted to an int (binary numeric promotion) to add 1.  So a becomes 97 (the ASCII value for 'a') and 98 results.
However, char1 += 1; or char1++ doesn't perform binary numeric promotion, so it works as expected.
Quoting the JLS, Section 5.6.2, "Binary Numeric Promotion":
(emphasis mine)
                        
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