Transcript Document

Agenda For April 2
1. PowerPoint Presentation on converting a String
into a number.
 http://members.shaw.ca/TextToNumber.ppt
2. Finish off ALL Mastery Questions.
3. Start Unit 6 Exercise.
Converting A String To a Number
Suppose you have declared and initialized a TextField called
myTextField.
Suppose you would like to retrieve the text information from this
textfield and do some mathematical calculations using its value.
In order to do this, you must perform the steps shown in the
following slide.
Converting A String To a Number Cont.
1. Decide what type of number (int or double) you will be
storing in the textfield and declare a new variable of that type.
2. Obtain the information from the textfield using the method
getText() and store it as a String variable.
3. Then use any one of the following methods to convert the
String into a number.
(a) Integer.valueOf(someString).intValue()
(b) Double.valueOf(someString).doubleValue()
4. Perform your mathematical computation using the number
value you obtained in step 3.
public class Gui extends Applet
{
TextField myTextField;
public void init()
{
setLayout(null);
myTextField = new TextField();
myTextField.setBounds(10, 50, 100, 20);
add(myTextField);
myTextField.setText(“5”);
}
public void myMethod()
{
// Step 1: declare a new variable
int num;
// Step 2: store the text in a string variable
String wordNum = myTextField.getText();
// Step 3: store the number value inside your variable
num = Integer.valueOf(wordNum).intValue();
// Step 4: use your variable in a calculation
num = num + 1;
}
}
Outputting Numbers In a TextArea
The two methods used for placing text in a TextArea only accept
variables of type String. Recall that these methods are:
1. setText(String)
2. append(String)
In order to output a number (integer or double value) to a
TextArea we use the same trick that was used to draw a number
to the screen.
An example is shown on the following slide.
import java.awt.*;
import java.applet.*;
public class Gui extends Applet
{
TextArea myTextArea;
public void init()
{
setLayout(null);
myTextArea = new TextArea();
myTextArea.setBounds(25, 50, 150, 100);
add(myTextArea);
myMethod();
}
public
{
int
int
int
void myMethod()
num1 = 5;
num2 = 3;
num3 = num1 + num2;
myTextArea.setText(“” + num1);
myTextArea.append(“ + ” + num2 + “ = ” + num3);
}
}