A DESCRIPTION OF THE PROBLEM :
According to https://docs.oracle.com/javase/10/docs/specs/jar/jar.html#name-value-pairs-and-sections empty new line always indicate a new section.

But still arbitrary header values should be allowed (even those containing empty lines). The empty lines are not properly escaped though (i.e. the leading space is missing) when using the regular Manifest.write(...) method.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Just execute the attached source code to see the problem.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
A valid manifest:
"
Manifest-Version: 1.0
Test: Some paragraph
 
 Another paragraph
"
ACTUAL -
An invalid manifest:
"
Manifest-Version: 1.0
Test: Some paragraph

Another paragraph
"

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import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.jar.Attributes;
import java.util.jar.Manifest;

public class ManifestTestWithEmptyLinesInAttributeValues {

    public static void main(String[] args) throws IOException {
        File tempFile = File.createTempFile("manifest", null);
        try {
            Manifest manifest = new Manifest();
            Attributes attributes = manifest.getMainAttributes();
            attributes.putValue("Test", "Some paragraph\n\nAnother paragraph");
            attributes.putValue(Attributes.Name.MANIFEST_VERSION.toString(), "1.0");
            try (FileOutputStream outputStream = new FileOutputStream(tempFile)) {
                manifest.write(outputStream);
            };
            try (FileInputStream inputStream = new FileInputStream(tempFile)) {
                manifest = new Manifest(inputStream);
            }
        } finally {
            tempFile.delete();
        }
    }

}

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FREQUENCY : always