Is it possible to access private fields in JAVA?

Question

Java

All hello, the question is the following, there is such a class

class ImmutableUserAgent implements UserAgent {
        private final String                            userAgentString;
        private final ImmutableAgentField               userAgentStringField;
        private final Map<String, ImmutableAgentField>  allFields;
        private final List<String>                      availableFieldNamesSorted;
        private final boolean                           hasSyntaxError;
        private final boolean                           hasAmbiguity;
        private final int                               ambiguityCount;

        public ImmutableUserAgent(MutableUserAgent userAgent) {
            userAgentString = userAgent.userAgentString;
            hasSyntaxError = userAgent.hasSyntaxError;
            hasAmbiguity = userAgent.hasAmbiguity;
            ambiguityCount = userAgent.ambiguityCount;

            userAgentStringField = new ImmutableAgentField(userAgentString, 0L, false, userAgentString);

            Map<String, ImmutableAgentField> preparingAllFields = new LinkedHashMap<>(userAgent.allFields.size());

The last line, i.e.

Map<String, ImmutableAgentField> preparingAllFields = new LinkedHashMap<>(userAgent.allFields.size());

refers to the allFields field of the MutableUserAgent class. The


question is, how is this possible, is it referring to the private field, is this possible in Java or am I not understanding something?

Answer 1

Through reflection
https://javarush.ru/groups/posts/513-reflection-ap...

Answer 2

Both classes (ImmutableUserAgent and MutableUserAgent) are nested in the UserAgent interface. And nested classes "see through each other".
For example, this also works:

public class C0 {

    class C1 {
        private String s;

        class C3 {
            private String s;
        }
    }

    class C2 {
        public C2(C1.C3 c3) {
            System.out.println(c3.s);
        }
    }

}

Why - do not ask :-) "So it happened historically" :-)))