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How would you write a constructor that checks that the array passed is the same length as the instance variable in the class?

I need to create a class that initializes the instance variable in it. In the if statement I am getting a Type mismatch error: cannot convert from int to boolean.
public class ProccessForm {
private String UserInfo[];
public ProccessForm(String[] UserInfo) {
UserInfo = new String[6];
if(UserInfo.length){
}
}

// if length of array passed does not equal length of current array
if (UserInfo.length != this.length) {
// do this
}
Right now in your if statement UserInfo.length returns an integer, if statements deal with Boolean logic so you need to use a conditional operator such as (<, >, <=, >=, ==, or !=) when working with primitives.

You are getting a type mismatch error because you're trying to compare an int value to a boolean value. The length field of primitive arrays returns an int data type and if blocks evaluate boolean value so you need to compare it with another object of the same raw type. Learn more about if-then and if-then-else statements as well as Arrays.
The following code should show you how your code should look like but there are a couple of more issues with your code that need to be addressed.
public class ProcessForm {
private String[] userInfo = new String[6];
public ProcessForm(String[] userInfo) {
if (this.userInfo.length == userInfo.length) {
// Do something here...
}
}
}
You should stick to a standard Java naming convention.
You also had a typo in the class name; process is spelled with a single c.
Java does not use C-style array declarations so you should declare your variable like this: String[] userInfo instead of String userInfo[] like you would in C language.
There is no need to initialize the class field inside a constructor when you're not using any parameter values in the initialization process. You can just declare and initialize it on the same line.
Remember to always use this keyword when you want to address class fields that have the same names as local variables otherwise you will be addressing local variables instead.

Do you have to store the value returned by conditional operator in java

I have a method , where I am doing a conditional operation.
But I get a compilation error.
public void hello(){
int x=15;
x==15 ?"Hi":"Bye";
}
If I edit the line and put something mentioned below , the error goes away:
String salutation=x==15 ?"Hi":"Bye;
My question is --is it mandatory to assign the value being returned by a conditional operator to a variable?

x==15 ? "Hi" : "Bye; just floating around does nothing; it's a pure expression. It's like just writing "Hi" in the middle of your code. You need to assign it to a variable for it to actually effect anything.
So yes, it's mandatory in the sense that if you want the ternary to do something, you must assign the result; providing no part of ternary (the condition, and both of the clauses) carries out side effects.

Do you have to store the value returned by conditional operator in
java
Not necessarily, but to simplify you cannot declare it without using it.
You may for example assign it to a variable as you did :
String salutation=x==15 ?"Hi":"Bye;
But you are not forced to store the value in a local variable.
You have other ways to use it.
You may for example pass it as a parameter that waits for a String :
myMethod(x==15 ?"Hi":"Bye");
public void myMethod(String string) {... }
Or you can still use it to apply a method on :
if ((x==15 ?"Hi":"Bye").equals("Bye")){
...
}

You are getting an error because you are not assigning the value based on the condition. Assigning a single variable to one of two states based on a single condition is such a common use of if-else that a shortcut has been devised for it, the conditional operator, ?:. you can't use the shorthand form ?: if the condition doesn't return any value. Your example can be rewritten
public void hello(){
int x = 15;
String salutation;
if (x == 15){
salutation = "Hi";
}else
salutation = "Bye;
}
Using the conditional operator we can rewrite the above example in a single line like this:
public void hello(){
int x = 15;
String salutation = x==15 ?"Hi":"Bye;
}

Java Output Variable Scope Issue

I have an issue regarding variable scope in the following piece of code. Can someone give a quick overview as to why java "cannot find the symbol" for output when it is printed? Thanks.
class Main
{
public static void main(String[] args) {
String text = "hello";
if (text.indexOf(" ") == -1) //if a space doesn't exist
{
String output = "one word";
}
else
{
String output = "more than one word";
}
System.out.println(output);
}
}

The variable output is only existent within the containing code block which currently seems to be within the if block and else block, if you want to access the variable output outside of the if and else block, you'll need to define it before the if block.

Local variables
A local variable is the one that is declared within a method or a constructor (not in the header). The scope and lifetime are limited to the method itself.
In addition to the local variables defined in a method, we also have variables that are defined in blocks, e.g. the if block and an the else block. The scope in this case is constrained by the block itself.

Inline braces block within method and loop [duplicate]

This question already has answers here:
Anonymous code blocks in Java
(11 answers)
Closed 9 years ago.
It's kind of hard to exactly search for this. I've seen this in a few places and I've even tried it in code to see how it works but just so that I know exactly how they can be used and to make sure I wont be abusing them I thought i'd ask on here.
public void doSomethingSpecial()
{
String strHello = null;
// What is the following section in braces for
{
strHello = "Hello World"
}
for(int i = 0; i < 10; i++)
{
// What is the significance of them it in a loop?
{
strHello = "Hello";
// Do something else...
}
.
.
.
}
}
Can someone clarify what these brace blocks braces are for?
I assume they work like a method and would restrict the scope of anything within as long as it isn't specified outside the block, but is there another use?
What is the exact name for them?
Thanks in advance

The braces define scope. For example, if you define a local variable within the braces and assign a value to it like this:
{
int foo = 10;
}
Then foo's scope (i.e. the section of code where it is define and has a value) is limited to the area within the braces.
The same goes for your for loop. Within those braces, the counter i is defined and has meaning, but not outside. So this code would not compile:
for (int i = 0; i < 5; i++) {
// Do something with i
}
i = 10; // Won't compile. i is undefined as a variable.
The benefits of this are numerous in that you can precisely control the scope for different variables. You can also define the scope of things like exceptions in the context of exception handling, etc.
You can also do things like this:
int i = 0;
for (; i < 5; i++) {
// Do something with i.
}
for (; i < 10; i++) {
// Do something else with i
}
In this case i is defined in a larger scope space (that of the enclosing method or constructor) and the for loops are only incrementing its value. So you are sharing a variable among two different areas of scope.
Lastly you can use them outside of a method or constructor as initialization blocks in a class. They allow you to initialize member variables that, for example, cannot easily be initialized with a single line of code.

Within the class, they form a static initializer, it runs once when the class is loaded, which happens first.
Within the method, they mark a scope. They are basically useless in your code.
But if the code is the following
{
String str = "test";
System.out.println(str);
}
{
System.out.println(str);
}
The second print will report a compilation error, since the scope of str is in the first scope.

So found something I thought I would post on here for anyone as none of the other questions seem to exactly clarify this.
When used outside of a method in class scope:
public class doSomethingSPecial() {
{
System.out.println("This is a constructor");
}
public doSomeThingSpecial() {}
public doSomethingSpecial(String specialString) { }
public doSomethingSpecial(int specialNumber) { }
}
"The Java compiler copies initializer blocks into every constructor. Therefore, this approach can be used to share a block of code between multiple constructors." - Java API Tutorial (Thanks to Soririous Delimanolis)
So the inline braces will be called each time a constructor is called.
As for the other questions regarding use within a method and loop the braces seem to be just to limit scope.
"In practice, though, if you find yourself using such a code block that's probably a sign that you want to refactor that block out to a method" - Credit to Robert Munteanu Top Answer: Anonymous code blocks in Java
That's basically everything I've come up with so far

Java: Catch uninitialized variable

Suppose we have a case where a variable is declared in certain conditions:
if (x = 1)
boolean z = true;
Later on, we'd like to test if the variable z exists with try-catch. Is this possible and if so, what exception should we catch?
try {
if (z)
//do smth
} catch (<exception?> ex) {
//do smth_else
}
Of course it would be possible to declare z before and change it's value accordingly in if block, but just hypothetically, is the above possible in Java?
Python for example has NameError that will be raised when accessed local or global variable is not declared.
Thanks!
HSI.

What if you declared your variable like this:
Boolean x = null;
In that case you could check for it being null or not.
An even better alternative would be using an enum to represent the uninitialized value:
public enum MyEnum {
UNINITIALIZED, TRUE, FALSE;
}
because if you will try to maintain your code several months later you (or someone else) may be puzzled about the Boolean being null.

we'll get compilation error if the variable we are using is not declared or is not visible in current scope.
If it is declared we can check for NullPointerException if that was object. In case of primitive data types we should check for default values.

Suppose we have a case where a variable is declared in certain conditions:
Well it is difficult to assume because that would not compile:
you should use == to test for equality
you can't declare a variable in an if statement unless there is a block
Now assuming you enclose that declaration inside a block, the scope of that variable would be that block and you wouldn't be able to use it in your try / catch block (unless it is inside the if block of course, but I don't think that's what you want).

No, this is not possible in Java. You have to have the variable declared before you can refer to it, otherwise you will get a compilation error.

Boolean z = null;
if (x = 1){
z = true;
}
if(z == null){
//not initialized
}else{
//initialized
}

it's not possible, Java is a strongly typed programming language because every variable must be declared with a data type before it can be used.
int x = 1;
boolean z = null;
if (x == 1)
z = true;
try {
if (z)
//do smth
} catch (NullPointerException npe ) {
//do smth_else
}

So far I understand , you wont be able to compile this piece of code. I can not remember any exception class but what I think is even if you "Invent" exception for this type of error. It won't compile. Because default values of primitive types are assigned to uninitialized class variables called fields but for variable used in method body, it gives compile time error