CODEWITHSUNDEEP
javaandroid
user13267
user13267

Reputation: 7193

how does implicit type conversion from integer to char work in Java (Java basics)

So in this basic Java program, 

public class HelloWorld{
    public void testFunc(){
        System.out.println("Class = "+this);
    }

    @Override
    public String toString(){
        return "TEST";
    }


    public static void main(String[] args){
        int i = 5;
        HelloWorld hw = new HelloWorld();
        System.out.println("Hello, World");
        hw.testFunc();
        System.out.println(i);
    }
}

the line System.out.println(i); automatically converts the int i into a String. I thought any function that requires a String type argument would automatically do this conversion in java (unlike in C). However, if I try this in Android
Toast.makeText(getApplicationContext(), i, Toast.LENGTH_SHORT).show();
where i declared as an int in the extended activity class, the app crashes upon launch. So how does this conversion work in Java?

Upvotes: 0

Views: 561

Answers (3)

Evgeniy Dorofeev
Evgeniy Dorofeev

Reputation: 136072

System.out.println(int) does convert int to char, it converts int to String using String.valueOf(int). Try explicit conversion System.println((char)i) and you will see that it prints a different result, it will be U+0005 Unicode character

Upvotes: 2

Nargis
Nargis

Reputation: 4787

To understand Type Conversions in JAVA:Refer

Every expression written in the Java programming language has a type that can be deduced from the structure of the expression and the types of the literals, variables, and methods mentioned in the expression.

It is possible, however, to write an expression in a context where the type of the expression is not appropriate. In some cases, this leads to an error at compile time. This holds true with Android Toast Example.

In other cases, the context may be able to accept a type that is related to the type of the expression; as a convenience, rather than requiring the programmer to indicate a type conversion explicitly, the Java programming language performs an implicit conversion from the type of the expression to a type acceptable for its surrounding context. And this holds true for System.out.println(i) Example

Upvotes: 1

rocketboy
rocketboy

Reputation: 9741

Its not an implicit conversion. The pintln() is overloaded by lots of datatypes:

public void println(int x) {
    synchronized (this) {
        print(x);
        newLine();
    }
}

And in your case makeText() is not.

Upvotes: 5

Related Questions