Java Community | Help. Code. Learn.•8h ago

prepping for an exam, new to java & might need help understanding some stuff

im just gonna put in questions here as I study ill probably not ask a whole ass program explanation unless its fully indecipherable to me ill bold whatever is the tldr version if you dont want extra context

30 Replies

JavaBot•8h ago

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Piglet | **NEED** tone tags!!•8h ago

firstly, whats a null literal 😭 ik it represents like no value but the text says "null is used to initialize an object of a class ... and may denote non-availability of a character in a String" secondly, ill need to do conversions from/to decimal, binary, hexadecimal and octal numbers but if anyone happens to know a method thats easy for any of that pls lmk

Piglet | **NEED** tone tags!!•8h ago

this is what we've been taught, I just have some trouble w I. & II. cuz im not great at calculations

dan1st•8h ago

null is a special value to indicate that there is no object. https://stackoverflow.com/a/19654040/10871900 The null literal is the text null that refers to that value

Stack Overflow

What is the difference between null, 0 and nothing?

What is the difference between null, 0 and nothing? I cannot find a question addressing all three of these. For example: If I am getting input from a string and parsing it to int. return Integer.

dan1st•8h ago

So every reference variable (so variables that are not primitives like boolean, char, short, int, long, float, double can be null meaning "no value associated with it" and you can explicitly set a variable to null using yourVariable = null; or check whether a variable is null using if(yourVariable == null) {}

dan1st•8h ago

Stack Overflow

What is null in Java?

What is null? Is null an instance of anything? What set does null belong to? How is it represented in the memory?

Piglet | **NEED** tone tags!!•8h ago

okay so like, its ONLY for non-primitive datatypes, but if I wanted to do pretty much the same thing w a primitive data type, smth like int example = 0 or String ex2 = "" works right

dan1st•8h ago

Integer.parseInt and Integer.toString, both support a radix specifying the base (e.g. 2 for binary, 10 for decimal, 16 for hexadecimal) https://docs.oracle.com/en/java/javase/21/docs/api/java.base/java/lang/Integer.html#parseInt(java.lang.String,int) https://docs.oracle.com/en/java/javase/21/docs/api/java.base/java/lang/Integer.html#toString(int,int)

Piglet | **NEED** tone tags!!•8h ago

oh I cant use code

dan1st•8h ago

The value 0 is a normal int and Strings are not primitive so a String can be null (which is usually not that good of an idea)

Piglet | **NEED** tone tags!!•8h ago

its a written exam, might have to write some programs but other than a simple calculator I cant use anything else okay, thanks

dan1st•8h ago

Well you can still use Integer.parseInt om your cpde

Piglet | **NEED** tone tags!!•8h ago

I mean the questions for that are gonna be like: "Convert 110101001 to hexadecimal" and id have to work it out myself

dan1st•8h ago

String hexadecimal = "A5";//a string with a number in hexadecimal
int convertedToInt = Integer.parseInt(hexadecimal, 16);//convert the hex (16) string to an int for further processing
String toBinary = Integer.parseInt(convertedToInt, 2);//convert the int to a binary (2) string
String toDecimal = Integer.parseInt(convertedToInt, 10);//convert the int to a decimal (10) string

String hexadecimal = "A5";//a string with a number in hexadecimal
int convertedToInt = Integer.parseInt(hexadecimal, 16);//convert the hex (16) string to an int for further processing
String toBinary = Integer.parseInt(convertedToInt, 2);//convert the int to a binary (2) string
String toDecimal = Integer.parseInt(convertedToInt, 10);//convert the int to a decimal (10) string

oh you mean without code? There are a few techniques for it

Piglet | **NEED** tone tags!!•8h ago

for program questions theyre like "A Piglatin word is the part of the word after the first vowel, the part before, added with an 'ay'" and I'd have to use like substring and loop commands to get that output yup

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prepping for an exam, new to java & might need help understanding some stuff