code: public synchronized <T extends Entry> T get(long index) {
      assertSegmentOpen();
      checkRange(index);
  
      // Get the offset of the index within this segment.
      long offset = relativeOffset(index);
  
      // Get the start position of the entry from the memory index.
      long position = offsetIndex.position(offset);
  
      // If the index contained the entry, read the entry from the buffer.
      if (position != -1) {
  
        // Read the length of the entry.
        int length = buffer.readInt(position);
  
        // Read the entry into memory.
        try (Buffer slice = buffer.slice(position + INTEGER, length)) {
          slice.read(memory.clear().limit(length));
          memory.flip();
        }
  
        // Read the checksum of the entry.
        long checksum = memory.readUnsignedInt();
  
        // Verify that the entry at the given offset matches.
        long entryOffset = memory.readLong();
        Assert.state(entryOffset == offset, "inconsistent index: %s", index);
  
        // Skip the term if necessary.
        if (memory.readBoolean()) {
          memory.skip(LONG);
        }
  
        // Calculate the entry position and length.
        int entryPosition = (int) memory.position();
        int entryLength = length - entryPosition;
  
        // Compute the checksum for the entry bytes.
        Checksum crc32 = new CRC32();
        crc32.update(memory.array(), entryPosition, entryLength);
  
        // If the stored checksum equals the computed checksum, return the entry.
        if (checksum == crc32.getValue()) {
          T entry = serializer.readObject(memory);
          entry.setIndex(index).setTerm(termIndex.lookup(offset)).setSize(length);
          return entry;
        }
      }
      return null;
    }
docs: Reads the entry at the given index.
  
  @param index The index from which to read the entry.
  @return The entry at the given index.
  @throws IllegalStateException if the segment is not open or {@code index} is inconsistent with the entry