java - 字符串类与其他类有何区别？

Question

我们可以做到:

String string = "ourstring";

但是我们不能为用户定义的类创建这样的对象:

用户类 uc="";

Java 如何允许我们仅将值直接设置到 java.lang.String 类？

Answer 1

java.lang.String 是一个特殊的类。

欢迎阅读 http://docs.oracle.com/javase/7/docs/api/java/lang/String.html

它说

The String class represents character strings. All string literals in Java programs, such as "abc", are implemented as instances of this class.

...

The Java language provides special support for the string concatenation operator ( + ), and for conversion of other objects to strings. String concatenation is implemented through the StringBuilder(or StringBuffer) class and its append method. String conversions are implemented through the method toString, defined by Object and inherited by all classes in Java. For additional information on string concatenation and conversion, see Gosling, Joy, and Steele, The Java Language Specification.

Java 语言没有其他类有这种特殊支持。

你应该非常小心它的 + 特性:它被广泛讨论为对性能和内存不安全。