Using Regex to parse String from input

Question

Here is my code to match a String like:

    String name = qualified.replaceAll(".*\\.(?=\\w+)", "");

Where it gets from input org.myapp.TestData$RootEntity a TestData$RootEntity

However I need to be able to get just the RootEntity part of the String. Effectively getting just this.

Input Strings:

com.domain.app.RootEntity

com.domain.app.TestData$RootEntity

com.domain.app.TestData$TestNested$RootEntity

And should be able to get RootEntity

Answer 1

Try this:

String name = qualified.replaceAll(".+?\\W", "");

.*\\\\W matches everything before $ or . and replaces it with empty string.

Answer 2

Try with simple String#lastIndexOf()

    String qualified = "org.myapp.TestData$RootEntity";

    String name = qualified.substring(qualified.lastIndexOf('$') + 1);

---

Complete code

    String[] values = new String[] { "com.domain.app.RootEntity",
            "com.domain.app.TestData$RootEntity",
            "com.domain.app.TestData$TestNested$RootEntity" };

    for (String qualified : values) {
        int index = qualified.lastIndexOf('$');

        String name = null;
        if (index != -1) {
            name = qualified.substring(qualified.lastIndexOf('$') + 1);
        } else {
            name = qualified.substring(qualified.lastIndexOf('.') + 1);
        }

        System.out.println(name);
    }

output:

RootEntity
RootEntity
RootEntity

Answer 3

简单：

String resultString = qualified.replaceAll("(?m).*?(RootEntity)$", "$1");

Answer 4

com.domain.app.RootEntity
com.domain.app.TestData$RootEntity
com.domain.app.TestData$TestNested$RootEntity

And should be able to get RootEntity

In looks like you want to remove each part of name which has . or $ after it like app. or TestData$ .

If that is the case you can try

replaceAll("\\w+[.$]", "")

---

Demo

String[] data = {
        "com.domain.app.RootEntity",
        "com.domain.app.TestData$RootEntity",
        "com.domain.app.TestData$TestNested$RootEntity",
};
for (String s:data)
    System.out.println(s.replaceAll("\\w+[.$]", ""));

Output:

RootEntity
RootEntity
RootEntity