这是因为字符串换行了。

有时你需要写一个长字符串。常见的错误是在字符串中输入了换行符。编译器就会报错：

Line nn: ; expected

当这种情况发生时, 解决方案是将字符串拆分为两个, 确保字符串中都没有新行, 并将它们与 + 连接起来。因此, 您可以替换:

原来：String s = A very long string which just happens to go over the end of a line and causes a problem with the compiler;

修改后

String s = A very long string which just happens to go over the end +of a line and causes a problem with the compiler

编辑器会提示

String literal is not properly closed by a double-quote

当我们编译时，报错

Example.java:4: 错误: 未结束的字符串文字

String s = A very long string which just happens to go over

^

Example.java:5: 错误: 需要;

我们把多行拼接起来，再次编译，就没报错了。