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众所周知
Java '+' 运算符用于两者
当我同时使用两者时，需要确切地知道预期的行为和应用的规则
当我尝试遵循 Java 代码时
System.out.println("3" + 3 + 3); // print 333 String concatenation ONLY
System.out.println(3 + "3" + 3); // print 333 String concatenation OLNY
System.out.println(3 + 3 + "3"); // print 63 Arithmetic Add & String concatenation
最佳答案
这是基本的运算符优先级，结合 String 连接与数字加法。
引用:
If only one operand expression is of type String, then string conversion (§5.1.11) is performed on the other operand to produce a string at run time.
The result of string concatenation is a reference to a String object that is the concatenation of the two operand strings. The characters of the left-hand operand precede the characters of the right-hand operand in the newly created string.
The String object is newly created (§12.5) unless the expression is a constant expression (§15.28).
An implementation may choose to perform conversion and concatenation in one step to avoid creating and then discarding an intermediate String object. To increase the performance of repeated string concatenation, a Java compiler may use the StringBuffer class or a similar technique to reduce the number of intermediate String objects that are created by evaluation of an expression.
For primitive types, an implementation may also optimize away the creation of a wrapper object by converting directly from a primitive type to a string.
参见语言规范 here .
长话短说
+ 的运算符优先级从左到右String，则结果是String关于算术加法和字符串连接之间的Java '+'运算符？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/38352779/
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