java正则表达式查找和替换

Question

我试图在输入中找到环境变量并用值替换它们.

env变量的模式是 ${\\.}

Pattern myPattern = Pattern.compile( "(${\\.})" );
String line ="${env1}sojods${env2}${env3}";

我怎么能代替env1用1和env2用2和env3用3,所以在此之后我将有一个新的字符串1sojods23？

Answer 1

Java中的字符串是不可变的,如果你在讨论需要查找和替换的任意数量的东西,这会使这有点棘手.

具体来说,你需要在定义你的替换Map,使用StringBuilder与StringBuffer和appendReplacements()方法的appendTail().最终结果将存储在您的Matcher.

Map<String, String> replacements = new HashMap<String, String>() {{
    put("${env1}", "1");
    put("${env2}", "2");
    put("${env3}", "3");
}};

String line ="${env1}sojods${env2}${env3}";
String rx = "(\\$\\{[^}]+\\})";

StringBuilder sb = new StringBuilder(); //use StringBuffer before Java 9
Pattern p = Pattern.compile(rx);
Matcher m = p.matcher(line);

while (m.find())
{
    // Avoids throwing a NullPointerException in the case that you
    // Don't have a replacement defined in the map for the match
    String repString = replacements.get(m.group(1));
    if (repString != null)    
        m.appendReplacement(sb, repString);
}
m.appendTail(sb);

System.out.println(sb.toString());

输出:

1sojods23

Answer 2

我知道这已经老了,我自己在寻找一个appendReplacement/appendTail例子,当我找到它时; 然而,OP的问题并不需要我在这里看到的那些复杂的多线解决方案.

在这种情况下,当要替换的字符串保持自己要替换的值时,可以通过以下方式轻松完成replaceAll:

String line ="${env1}sojods${env2}${env3}";

System.out.println( line.replaceAll("\\$\\{env([0-9]+)\\}", "$1") );

// Output => 1sojods23

DEMO

当根据每个匹配的某些条件或逻辑替换是随机的时,您可以使用appendReplacement/appendTail例如

Answer 3

希望您会发现此代码有用：

    Pattern phone = Pattern.compile("\\$\\{env([0-9]+)\\}");
    String line ="${env1}sojods${env2}${env3}";
    Matcher action = phone.matcher(line);
    StringBuffer sb = new StringBuffer(line.length());
    while (action.find()) {
      String text = action.group(1);
      action.appendReplacement(sb, Matcher.quoteReplacement(text));
    }
    action.appendTail(sb);
    System.out.println(sb.toString());

输出是预期的：1sojods23。

Answer 4

这给你1sojods23：

String s = "${env1}sojods${env2}${env3}";
final Pattern myPattern = Pattern.compile("\\$\\{[^\\}]*\\}");
Matcher m = myPattern.matcher(s);
int i = 0;
while (m.find()) {
    s = m.replaceFirst(String.valueOf(++i));
    m = myPattern.matcher(s);
}

System.out.println(s);

这也有效：

final String re = "\\$\\{[^\\}]*\\}";
String s = "${env1}sojods${env2}${env3}";
int i = 0;
String t;
while (true) {
    t = s.replaceFirst(re, String.valueOf(++i));
    if (s.equals(t)) {
        break;
    } else {
        s = t;
    }
}

System.out.println(s);

Answer 5

匹配后使用组${env1}将是您的第一个组，然后使用正则表达式替换每个组中的内容。

Pattern p = Pattern.compile("(${\\.})");
Matcher m = p.matcher(line);
while (m.find())
  for (int j = 0; j <= m.groupCount(); j++)
    //here you do replacement - check on the net how to do it;)