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If-else One line statement (with string and integer) [closed]

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I'm creating a program. This code below is the Java program. Checking if the value of B and H, input by the user is equal to zero. If it is true, then a math formula will execute which is p = b*h then if it is false, a string will be shown on the console. But the thing is, it keeps on giving me an error that string cannot be converted to int or int cannot be converted to string.
Here is the code:
import java.util.Scanner;
public class StaticProject{
static {
Scanner input = new Scanner (System.in);
int B = input.nextInt();
int H = input.nextInt();
int P;
int solution = B>=0 && H>=0 ? P = B*H : "java.lang.Exception: Breadth and height must be positive";
}
How can I improve my coding when it comes in doing this oneline bi-conditionals statement? Any tips?

your solution variable Type is int, and your else statement returns an String, this is the cause of error.
you can change your code to this:
Scanner input = new Scanner (System.in);
int B = input.nextInt();
int H = input.nextInt();
int P;
if (B >= 0 && H >= 0) {
P = B*H;
} else {
throw new Exception("Breadth and height must be positive");
}
System.out.println(P);
}

You are trying to assign string to an int variable, if your statement is evaluated as false.
You need to use if/else condition, which both sides have the same type.
In your case, it's not possible.
another possibility is use System.out.println() command, to print the result of whatever resulted by the condition.

There is no virtue in writing code in as few lines as possible. By all means, don't write unnecessary code, but just don't think that concise code is objectively "better".
The best type of code to write is simple code. Maybe it's a little more verbose; but if you write code that people can understand at a glance, they know what it does straight away.
Here is how I would write it:
if (B < 0 || H < 0) {
// Actually, non-negative, rather than positive.
throw new Exception("Breadth and height must be positive");
// Or, maybe, don't even use exceptions at all:
// System.out.println("The message");
// return;
}
// No need for `solution` variable.
P = B * H;
System.out.println(P);
Of course, you might argue this isn't code everybody will understand at a glance. Sure. Readability is subjective; but I assert that anybody with just a little bit of experience in Java can work it out.
You can write a conditional ?: expression which results in an exception being thrown in the case of the condition being false.
// Define a method which does the throwing.
static int justThrow(String message) throws Exception {
throw new Exception(message);
}
// In the main method:
int solution = B>=0 && H>=0 ? P = B*H : justThrow("Breadth and height must be positive");
I emphasize that you can, but you shouldn't do this. It's obscure. It's trying to be "a bit too clever". It will have people reading your code and scratching their heads, because they will wonder why you wrote a method for something so simple; what is the solution variable for, given that it will have the same value as P etc.

Java String comparison wrong outcome [closed]

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I am trying to get a Save button to enable/disable based on if the EditTexts actually change, but my string comparison is not working at all.
public void afterTextChanged(Editable editable) {
String newSet = editable.toString();
newSet = newSet.trim();
if(!newSet.equals(ip) || !newSet.equals(port) || !newSet.equals(username) || !newSet.equals(password)){
saveButton.setEnabled(true);
}else{
saveButton.setEnabled(false);
}
}
It keeps telling me the strings are different even though they aren't. Even when I print it out I get exactly the same String back.
Can anyone help me?
Thanks

Probably you want && instead of ||:
public void afterTextChanged(Editable editable) {
String newSet = editable.toString().trim();
saveButton.setEnabled(!newSet.equals(ip) &&
!newSet.equals(port) &&
!newSet.equals(username) &&
!newSet.equals(password));
}
enable saveButton if newSet is not a ip, port, username or password

You should write it like that, way easier to read :
if (!Arrays.asList(ip, port, username, password).contains(newSet))
{
saveButton.setEnabled(true);
}
else
{
saveButton.setEnabled(false);
}
Or :
saveButton.setEnabled(!Arrays.asList(ip, port, username, password).contains(newSet));

newSet can't be equal to all four of these Strings, unless all 4 are equal to each other. Therefore the condition will most likely return false.
If you require that newSet be equal to either one of those 4 Strings, the correct condition would be :
if(!(newSet.equals(ip) || newSet.equals(port) || newSet.equals(username) || newSet.equals(password)))

replace || with &&
if(!newSet.equals(ip) && !newSet.equals(port) && !newSet.equals(username) && !newSet.equals(password))
Reason :
OR(||) If any condition get satisfied it will enter inside the loop.
AND(&&) If all conditions get satisfied then and then only it will enter inside the loop.
In your case you need to satisfy all the conditions, that's why use and operator instead of or operator.

Java int 'through' int operator? [closed]

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I'm trying to figure out how to do something like:
int test = 1;
int test1 = 10;
if (value = test (though) test1) {
}
I've looked at oracles java operators but could not figure out how to do it.
The construct should check if value is between test and test1.
Can anybody tell me how to do this in Java?

if (value >= test && value <= test1)
{
//doSomething
}
Java does not support chained inequalities, ie test <= value <= test1, so instead you can just use two boolean expressions, connected via the boolean and operator, to get a logically equivalent conditional.

You should try something like with logical and operator
if (value > test && value < test1) {
// do something
}
or add >= to add equals comparison too.

It looks like you are looking for range operator that is common in a lot of programming languages, Java not being one of them, but the condition that you are trying to impose on the range will always be the same. You don't need to check every value in the range, merely the endpoints since it is contiguous:
if( value > test && value < test1 ) {
// do something
}

There is no through op in Java. You can do it with a simple if :
if (value >= test && value <= test1) {
// your code
}

This post begged to be clarified.
If you are checking that value is between test1 and test2 then you need:
if(value >= test && value <= test1){
// do stuff
}
Note that you should remove the = signs if value should be strictly between test and test1.
However, if you are checking that value is one of multiple tests from test0 "through" test10 for instance, then pack those tests in a set and check if value is among them:
import java.util.*;
Set tests = new HashSet();
tests.add(test);
tests.add(test1); // similarly for as many as you need
if(tests.contains(value)){
// do stuff
}

Error when check an empty element in array [closed]

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why cannot I check if a place in array is empty ?
I got this wrong message:
The operator == is undefined for the argument type(s) int, null"
on the marked line
private static int findNr(int[] trans)
{
int emptyPlace=0;
for (int i=0; i<trans.Length -1;i++)
{
--> if( trans[i] = null) <--
return emptyPlace = trans[i];
}
return emptyPlace;
}

You can not compare primitive data type for null. int is primitive data type.

You have to do
if( trans[i] == null)
instead of
if( trans[i] = null)
^-----------Mistake
Anyway in which language you have written the code?

You try to assign null to the array element at position i
To check if the element is null you have to do:
if(trans[i] == null)
{
...
}
but this expression doesn't make any sense since an int can never be null (unless its a nullable int (int?)) so the condition will always be false

Primitive cannot be checked with the null. So for particular primitive types use their default value to check.
i.e for int default value is 0 and for
double default value is 0.0 etc.
So check as:
if(intr[i]==0){
//some logic
}

if( trans[i] = null)
In the above line your are using assignment operator = in place of comparison operator ==. If condition expects the final value after computation to be of the type boolean. Hence you get the error.
Also your trans[i] is an primitive int value which cannot be compared to a null. (Only objects can be null in java)
The assignment operator = will only work in case of boolean variables, something like this:
boolean flag = false;
if(flag=true) {
// this condition will be true
}

First, you mispelled the == comparison. Should be:
if (trans[i] == null)
Second, the above doesn't works. Primitive values can never be null, when you declare any int variable, it's 0 by default.
Thats why:
int[] v = new int[3];
for (int i = 0; i < v.length; i++)
System.out.println(v[i]);
Outputs this:
0
0
0
You should either work with Integer objects array or review your logic.

1- You have forgot '=' ---> if (trans[i] == null)
2- You can't compare primitive value (int) with null

Java: NullPointerException with substrings [closed]

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I'm having a problem in one of my methods. Please keep in mind that I am learning Java in college so I might not be up to speed on simple things. Below is a method that is made to add expressions. The problems I'm running into is found where x = x.substring.(1, x.length() - 1); I'm getting an exception that reads:
Exception in thread "main" java.lang.NullPointerException
I have no idea what that means and/or how to fix it. If you could point me in the right direction, that'd be great.
Thanks.
public static int adder(String x){
int total = 0;
x = x.substring(1, x.length() - 1);
sopln(x);
String[] nums = x.split("\\+");
for(int i = 0; i < nums.length; ++i){
if(nums[i].charAt(0) == ' ' || nums[i].charAt(nums[i].length()-1) == ' '){
sopln("ERROR: Excess whitespace identified.");
nums[i] = nums[i].trim();
}
nums[i] = nums[i].replaceAll(" ", "");
if(nums[i].charAt(0) == '-')
total -= Integer.parseInt(nums[i]);
else
total += Integer.parseInt(nums[i]);
}
return total;
}

It probably means that your String x is null and not actually set to an Object of a String.
How are you calling the method?
Does it happen when you call it with a hard coded string like
int num = adder("string checking in");
if not, then somewhere upstream in your code, that String variable you are passing into the adder method is null.

you are passing a null value when you call adder(the_string), where the_string is null

The problems I'm running into is found where x=x.substring.(1,x.length() - 1);
This means that at some point you are calling adder with an argument that is null. That's the only way you can get an NPE at that point.
Find out where and why the argument is null, and then fix it.
(It could be an explicit null, but it is more likely to be coming from an uninitialized field, or from some method that returns a null to indicate something; e.g. BufferedReader.readLine() returns null when the reader reached the EOF position.)