What is the issue with this if statment? [duplicate]

This question already has an answer here:

• Why is my c != 'o' || c != 'x' condition always true? 5 answers

I am having an issue with this if statement with multiple conditions. I do know for a fact that the individual conditions run fine, only when they are together does it have issues. Specifically the issue is that it will return false even though the condition is met and if i ungrouped it with the same input it would work.

if(dnaArray[i] != "a" || dnaArray[i] != "c"|| dnaArray[i] != "t" || dnaArray[i] != "g")

Also i'm sorry if this isn't exact to the guidelines, if there is an issue just let me know and I will fix it.