java ReplaceAll 和 " 不更换
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ReplaceAll and " doesn't replace
提问by Hannelore
Can anyone point me out how the first if works and the second doesn't? I'm puzzled why the second if-clause isn't working. I'd like to get a hint, thanks.
谁能指出我第一个 if 是如何工作的，而第二个则没有？我很困惑为什么第二个 if 子句不起作用。求指点，谢谢。
String msg = o.getTweet();
if (msg.indexOf("&") > 0) {
msg = msg.replaceAll("&", "&");// vervangt & door &
}
if (msg.indexOf(""") > 0) {
msg = msg.replaceAll(""", "aa"); //vervangt " door "
}
回答by Adeel Ansari
Because ZEROis a very validindex. Try this out,
因为ZERO是一个非常有效的索引。试试这个，
String msg = o.getTweet();
if (msg.indexOf("&") != -1) {
msg = msg.replaceAll("&", "&");// vervangt & door &
}
if (msg.indexOf(""") != -1) {
msg = msg.replaceAll(""", "aa"); //vervangt " door "
}
Explanation:
解释：
The documentation of String.indexOf(String str)explains that, "if the string argument occurs as a substring within this object, then the index of the first character of the first such substring is returned; if it does not occur as a substring, -1 is returned."- [link to docs]
的文档String.indexOf(String str)解释说，“如果字符串参数作为此对象中的子字符串出现，则返回第一个此类子字符串的第一个字符的索引；如果它不作为子字符串出现，则返回 -1。” - [文档链接]
This can be done as simple as below, as OpenSaucepointed out here.
正如OpenSauce在此处指出的那样，这可以像下面一样简单地完成。
msg = msg.replace("&", "&").replace(""", "\"");
Useful links:
有用的链接：
回答by OpenSauce
You don't need to check the substring exists, the replaceand replaceAllmethods are no-ops if the substring is not found. Since you're not looking for regexes, you can also use replaceinstead of replaceAll- it will be somewhat more efficient, and won't surprise you if you also want to check for other strings which happen to contain regex special chars.
您不需要检查子字符串是否存在，如果未找到子字符串，则replace和replaceAll方法是无操作的。由于您不是在寻找正则表达式，因此您也可以使用replace代替replaceAll- 它会更有效率，并且如果您还想检查其他碰巧包含正则表达式特殊字符的字符串，您也不会感到惊讶。
msg = msg.replace("&", "&").replace(""", "\"");
note that replacedoes indeed replace allmatches, like you want. The difference between replaceand replaceAllis whether the arg is interpreted as a regex or not.
请注意，replace确实会替换所有匹配项，就像您想要的那样。replace和之间的区别在于replaceAllarg 是否被解释为正则表达式。
