If a zip implementation writes a zip file with exactly 0xFFFF entries, then it is within its rights to write a non-ZIP64 zip file. But some JDK code assumes that the presence of 0xFFFF in the zip end of central directory header indicates the presence of a ZIP64 header, failing when one cannot be found. This is a regression.

SSCCE:

 (set -x; cat FFFF.java; cat Main.java; ~/jdk/jdk6/bin/javac Main.java FFFF.java && ~/jdk/jdk6/bin/java FFFF && for x in 6 7 8 9; do ~/jdk/jdk$x/bin/java -jar ffff.zip ; done)
+/bin/zsh:19> cat FFFF.java
import java.io.*;
import java.util.*;
import java.util.zip.*;
import java.util.jar.*;

public class FFFF {
    public static void main(String[] args) throws Throwable {
        File f = new File("ffff.zip");
        OutputStream os = new FileOutputStream(f);
        ZipOutputStream s = new ZipOutputStream(os);

        ZipEntry man = new ZipEntry("META-INF/MANIFEST.MF");
        s.putNextEntry(man);
        s.write("Manifest-Version: 1.0\n".getBytes("US-ASCII"));
        s.write("Main-Class: Main\n".getBytes("US-ASCII"));
        s.closeEntry();

        ZipEntry main = new ZipEntry("Main.class");
        s.putNextEntry(main);
        byte buf[] = new byte[10000];
        int n = new FileInputStream("Main.class").read(buf);
        s.write(buf, 0, n);
        s.closeEntry();

        for (int i = 0; i < 0xffff -2; i++) {
            ZipEntry e = new ZipEntry(String.valueOf(i));
            s.putNextEntry(e);
            s.closeEntry();
        }

        s.close();
    }
}
+/bin/zsh:19> cat Main.java
import java.util.*;

public class Main {
    public static void main(String[] args) {
        System.out.println("Main ffff");
    }
}
+/bin/zsh:19> /usr/local/google/home/martinrb/jdk/jdk6/bin/javac Main.java FFFF.java
+/bin/zsh:19> /usr/local/google/home/martinrb/jdk/jdk6/bin/java FFFF
+/bin/zsh:19> x=6
+/bin/zsh:19> /usr/local/google/home/martinrb/jdk/jdk6/bin/java -jar ffff.zip
Main ffff
+/bin/zsh:19> x=7
+/bin/zsh:19> /usr/local/google/home/martinrb/jdk/jdk7/bin/java -jar ffff.zip
Main ffff
+/bin/zsh:19> x=8
+/bin/zsh:19> /usr/local/google/home/martinrb/jdk/jdk8/bin/java -jar ffff.zip
Error: Invalid or corrupt jarfile ffff.zip
+/bin/zsh:19> x=9
+/bin/zsh:19> /usr/local/google/home/martinrb/jdk/jdk9/bin/java -jar ffff.zip
Error: Invalid or corrupt jarfile ffff.zip