If you have many expressions or long expressions, you could parse them as text by putting them in a text file, then scanning through it using Scanner. By the way, this is a fascinating question, glad you asked!
File expressions = new File(/*pathname*/);
File inverse = new File(/*pathname*/);
FileWriter fileWriter = new fileWriter(inverse);
Scanner scanner = new Scanner(expressions);
while(scanner.hasNext()){
String str = "";
String next = scanner.next();
if (next.equals("=="){
str = "!=";
}
else if (next.equals("!="){
str = "==";
}
else if (next.equals("||"){
str = "&&";
}
else if (next.equals("&&"){
str = "||";
}
fileWriter.write(str)
}
This almost surely works, maybe the suggestion Tim made is better.
Like Tim said, your goal will likely be accomplished through some sort of parsing.
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