Does two lines of copied code constitute plagiarism?
It appears strongly likely that you did plagiarise, and if this is the case you'd be better to proceed by recognising your mistake than continuing to argue.

Looking at your code, there is a great deal that appears to have been taken from the HashMap.java file. I strongly suspect that you began with this code and then modified it to produce your code, or closely followed it as a template when writing your own. The highlighted code sections have picked up some of this, but other sections closely resemble the other file too, although with slightly altered comments and ordering.

If this is the case, then the code you have shown us is not your own original work but actually a plagiarised version of HashMap.java. Leaving in the two lines which are unconnected is a smoking gun of the link that is likely to be conclusive to the panel. Your point that they are unnecessary will actually count against you because you will be unable to explain why they are there at all.  And whether this was your intent or not, it is likely that the panel (and your professor) will see your changed comments and ordering as an attempt to cover up your tracks and conceal your plagiarism from automated tools.

The panel is more likely to show leniency towards a student who appears to at least be contrite, and recognises that they've made a mistake, than a student who denies wrong-doing in the face of apparently very strong evidence.