Regex to print implementing interfaces from a Java source file

Question

I have a bunch of java source files and want to list the interfaces implemented by each class in the sources.

The best case is when a class is declared in one line

class MyClass implements MyInterfaceA, MyInterfaceB {

However, there are classes that are declared in multiple lines

class SomeClass 
     implements
        InterfaceC,
        InterfaceD
        {

So, basically, if I can have a regex that can capture everything between the first implements string literal and the first occurrence of character {, I have the names of implementing interfaces.

For the last hour or so, I've been tinkering with several tools like grep, pcregrep, sed and awk and finally arrived at one command that seems to work.

pcregrep -M 'class[\s\S]*implements'

As you can see, I am trying to output everything between the words class and implements and the command outputs the lines

class SomeClass 
     implements

When I modify the same expression to output everything between implements and {, it outputs much more than I require, perhaps because there are so many { in the file and/or because { is a special character.

How do I output just the text between the first implements and the first { after that?

RomanPerekhrest · Accepted Answer · 2017-10-02 17:50:18Z

1

With GNU grep:

Sample input.java file:

class MyClass implements MyInterfaceA, MyInterfaceB {
}
class SomeClass 
     implements
        InterfaceC,
        InterfaceD
        {
}

The job:

my_interfaces=$(grep -Poz '\bimplements[[:space:]]*\K[^{]*(?=\{)' input.java | tr -s '\n' ' ')
echo "$my_interfaces"

The output:

MyInterfaceA, MyInterfaceB InterfaceC, InterfaceD

answered Oct 2, 2017 at 17:50

RomanPerekhrest

93.1k4 gold badges75 silver badges112 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

Regex to print implementing interfaces from a Java source file

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related