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Java Forum / General / July 2006String to Long and then to String
I have a String: "This is a test" and I need to convert it into a long value. Then I need to convert the long value back to the original String. Can I use: long test = Long.valueof("This is a test"); String string = Long.valueof(test).toString(); Now string is: "This is a test"? If not, any better way to do it? >I have a String: "This is a test" and I need to convert it into a long > value. Then I need to convert the long value back to the original [quoted text clipped - 5 lines] > > Now string is: "This is a test"? If not, any better way to do it? Explain "convert to a long" and we could probably help you. valueof function does not convert strings to numbers. IT does convert decimal representation to a computer number. "This is a test" assuming a 27 letter alphabet has a high digit of 27^13 giving you an effective range of 0 - 109418989131512359208 (27^14 - 1). You will notice that this exceeds the holding capacity of a long. First . . WHY are you converting a string to a long. And if you know why, then HOW do you want it converted (it's ok if you don't know the how part, as long as you can get the why part we can probably help you)? -- LTP :) Thanks for the help. Basically I need to call a function and that function only takes a "long" arg. But I only have a String. That's why I want to convert the String into "long" and then inside the function, I convert the "long" back to the original String...It doesn't even sound right but I don't have a better solution since I can't change the function signature... > >I have a String: "This is a test" and I need to convert it into a long > > value. Then I need to convert the long value back to the original [quoted text clipped - 23 lines] > > :) > Thanks for the help. > [quoted text clipped - 3 lines] > back to the original String...It doesn't even sound right but I don't > have a better solution since I can't change the function signature... The simple answer is: You probably do not want to call that function with a representation of a String, since obviously the function is not designed for that. It doesn't do what you want, and you either have to use a different one, or make your own. It's impossible to say which, given that you haven't answered Luc's question yet: WHY. Don't say what solution you picked, say what you want to do.  SignatureFrank > Basically I need to call a function and that function only takes a > "long" arg. But I only have a String. That's why I want to convert the > String into "long" and then inside the function, I convert the "long" > back to the original String...It doesn't even sound right but I don't > have a better solution since I can't change the function signature... This comes up when trying to extend certain scripting languages in C. The usual solution is pass the function a pointer to the object, in this case the string. This is theoretically non-portable, because of the pointer/long conversions, but it works in practice. Are you using JNI? Do you have the source code for the function you are calling? Or even API documentation for what it's supposed to do? If so, it would help if you posted it. If the input to the function is a long, it is probably doing something mathematical, like calculating a cube root. In that case, it makes no sense to take the cube root of "dog" or "this is my string", even if you convert it to a long. Perhaps you are using the wrong function entirely?? -- Rhino > Thanks for the help. > [quoted text clipped - 31 lines] >> >> :) > Thanks for the help. > [quoted text clipped - 3 lines] > back to the original String...It doesn't even sound right but I don't > have a better solution since I can't change the function signature... It is not possible to convert general string value to long in a way that string keeps it's content. Bu, maybe, you could try with some kind of two way dictionary. ArrayList longToString; HashMap stringToLong; .... longToString=new ArrayList(); stringToLong=new HashMap(); .... long toLong(String s) { Object o=stringToLong(s); if(o == null) { longToString.add(s); long lng=(long) (longToString.size() -1); stringToLong.put(s,new Long(l)); return lng; } return ((Long)o).longValue(); } ..... Be carefull of multithreaded access, you might want to make method synchronized. DG > I have a String: "This is a test" and I need to convert it into a long > value. Then I need to convert the long value back to the original > String. Why? > Can I use: > long test = Long.valueof("This is a test"); > String string = Long.valueof(test).toString(); > > Now string is: "This is a test"? If not, any better way to do it? Use a counter and some kind of lookup structure you can store strings in. Increment the counter with each new string and store counter,string pair. 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