java如何处理字符串文字 [英] how java handles string literals

问题描述

在java中，我创建了2个具有相同值的字符串文字

in java, i have created 2 string literals having same value

String a = "Hello";
String b = "Hello";

现在两者都应该有相同的参考

now both of them should have same reference

System.out.println(a==n); // returns true

但是当我这样做时

b+=" World";
System.out.println(a==b); // returns false

现在我有2个问题在这里

1.为什么a 'b + ='操作后，b不引用同一个对象？
2.为什么我能更改字符串b而没有任何错误？（因为我读过String类是不可变的）

Now i have 2 questions here
1. why a and b are not referencing to same object after 'b+=' operation? 2. how come i'm able to change string b without any error?(because i have read String class is immutable)

推荐答案

您可以更改 b 的原因是因为您在技术上制作了一个新的String对象并将其分配给现有的引用。

The reason you can change b is because you're technically making a new String object and assigning it to the existing reference.

b += " World"

与

b = b + " World";

b 技术上指向一个新字符串宾语。首先， a 和 b 指向同一个对象，但是当 b时被修改它现在是一个不同的对象，所以 a 将不等于Hello World和 a == b 现在将为false。

b is technically pointing to a new String object. So to start out, a and b are pointing to the same object, but when b is modified it is now a different object, so a will not equal "Hello World" and a==b will now be false.

有关可变String类的示例，请尝试 StringBuffer 或 StringBuilder 。您可以使用他们的 .append（）方法添加到字符串中，以及其他方法来修改它。

For examples of mutable String classes, try StringBuffer or StringBuilder. You can use their .append() method to add to the string, along with other methods to modify it.

这篇关于java如何处理字符串文字的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！