Difference between revisions of "Java/C2/Primitive-type-conversions/English"

Welcome

Learning Outcomes

• How to convert data from one data type to another.
• the two types of conversion, namely implicit and explicit conversion.
• How to convert strings to numbers

Tools Used

• Ubuntu 11.10
• JDK 1.6
• Eclipse 3.7

Prerequisites

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Type Conversion

Let us see how it it done.

Switch to Eclipse

Eclipse should contain the following code

public class TypeConversion

{

public static void main(String[] args)

{

}

}

I have created a class TypeConversion and added the main method to it.

Now let us create a few variables.

int a = 5;

float b;

b = a;

System.out.println(b);

float b

b equal to a

I have created two variables. a which is and integer and b which is a float.

I’m storing the integer value in a float variable.

Let us see what the float variable now contains.

System dot out dot println b '

Save the file and run it.

This type of conversion is called implicit conversion.

As the name goes, the value is automatically converted to suit the data type.

Now let us convert float to an int, using the same method.

Change b to b = 2.5f;

Change b = a to a = b;

Change b to a inside println

Point to the cross mark on left.

Save the file.

 we   see that there is an error.

The error message reads, Type mismatch: cannot convert from float to int

It means Implicit conversion is possible only from an int to a float but not the the other way.

To convert a float to int we have to use explicit conversion.

Let us see how to do so.

and point to that line

This statement says the data in the variable b has to be converted to int data type and stored in a.

As we can see, the float value has been converted to int.

But to suit the data type, the data has been changed accordingly.

Explicit conversion can also be used to convert data from int to float.

Let us try anthe previous example.

Change float b = 2.5f to float b;

Change a = (int) b to b = (float) a;

Change println(a) to println(b)

save and run. Point to output

System.out.println(b); We are using Explicit conversion to convert integer to a float

Save the file and Run it.

we  see that   the int value has been converted  to  a float value 

Let us see what happens when we convert a character to integer.

char c = 'm';

int a;

a = (int) c;

System.out.println(a);

' a equal to (int) c;

System dot out dot println ' a.

We are convewrting character m to an integer and printing the value Let us save and run it

It means when a char is converted to int, its ascii value is stored.

Let us try this with a digit.

Save it and run it 

It is not the number 5.

To get the number, we have to use a string and convert it to an integer.

Now let us see how to do so.

String sHeight = “6”;

int h = (int) sHeight;

System.out.println(h);

type

String sHeight equal to in double quotes 6 semicolon.

int h equal to explicit conversion to int of sHeight and System dot out dot println h Save the file.

I’ve created a string variable with value 6 and i am trying to convert it to an integer but we see that their is an error

This means for converting strings, we cannot use implicit or explicit conversion.

It must be done by other methods. let us use them

int h = Integer.parseInt(sHeight);

Save the file and run it

To do this we use the parseInt method of the integer module. Now let us see what happens if their are more than one digits like 6543

Save the file and run it

We see that again strings contain the number has been successfully converted to an integer

Now let us see what happens if the strings is a floating point number Change 6543 to65.43.So we have a floating point number in the string and we are converting it to an integer Save the file run it.

We have to convert it TO  afloat.Let us see how to do so;

First data type should be float, Second we will use float . parsefloat, We are using the Parsefloat methods of the float class to convert the string containing a floating point number into an actual floating point number. Save the file run it. We can see the string containing a floating point number has been successfully converted into floating point number. And this is how we do implicit and explicit conversion and How do we converts strings to numbers

Slide 6

Summary

In this tutorial we have learnt how to convert data from one type to another. What is meant by implicit explicit conversin and How to convert strings to numbers.

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