What's the difference between these 2 statements?

What's the difference between this:

if(codons[i] == "UCU" || codons[i] ==  "UCC"|| codons[i] ==  "UCA"|| codons[i] ==  "UCG")

and:

if(codons[i] == "UCU" || "UCC"|| "UCA"||"UCG")

What's the logic behind how each of those statements are interpreted?