In this section, we will write the code for the HelloWorld application. We will use the following tools:
- Code completion. The Source Editor parses all of the packages and classes in the classpath, including the standard JDK classes, and automatically suggests matching packages and classes as you type.
- Abbreviations. The IDE includes abbreviations for many commonly used word combinations that expand to the full words when you press Space. For example, typing psf and pressing Space expands the abbreviation to public static final.
- Fast Import. The Source Editor lets you automatically generate the import statement for any class.
- Automatic formatting and error highlighting.
When you are done with this section, HelloWorld.java will look like this:
/*
* HelloWorld.java
*
* Created on 16 November 2004, 11:52
*/
package hello;
import java.util.Date;
/**
*
* @author me :-)
*/
public class HelloWorld {
/** Creates a new instance of HelloWorld */
public HelloWorld() {
}
/**
* @param args the command line arguments
*/
public static void main(String[] args) {
String date = new Date().toString();
System.out.println("Hello world! It's " + date);
}
}
- Place the cursor at the end of the public static void main(String[]
args) { line and press Enter.
- Type String date = new Dat and wait. Within a second or two,
the code completion box should appear, listing all of the JDK classes
that begin with Dat. You can also manually open the code completion
box by pressing Ctrl-Space.
The Source Editor also shows the Javadoc description of each class, if available. The IDE extracts this description from the Javadoc comments in the source code. For more information on working with Javadoc documentation, see the Using NetBeans IDE guide. - In the code completion box, scroll down to Date. Notice there
are two Date classes in the classpath. Select either of the
two and press Enter. - u
Note: Unless you use a fully-qualified name for a class, the code completion box offers the methods of all classes with the same name. It therefore does not matter whether you choose java.sql.Date or java.util.Date from the code completion box in the step above. - Type (. Notice the IDE automatically fills in the closing parentheses.
- Go to the end of the line and type a . after the closing parentheses. The code completions box opens listing all of the methods in the Date class. Deprecated methods are shown with a line crossed through them. Start typing toString to narrow the selection down, then select toString and press Enter.
- Type a closing ;.
- Notice that the line you just entered is underlined with a red line
and has a
icon in the left margin, meaning that it contains errors. - Hold the mouse over the icon to view the error. Since you have not entered an import statement for the Date class, the file contains a cannot resolve symbol compilation error.
Create import statement
- Place the insertion point anywhere in the word Date and press Alt-Shift-I.
- In the Fast Import dialog box, choose java.util.Date and click OK. The import statement is created and the Source Editor no longer shows an error for the line.
Expand abbreviations
- Place the cursor at the end of the String date = new Date().toString(); line and press Enter.
- Type sout and press Space. The sout abbreviation expands to System.out.println("");
- Type Hello World! It's between the quotation marks (be sure to include a space after It's).
- After the closing quotation mark, type + date.
Reformat code
- If the spacing for the comment line does not match the spacing for the rest of the file, press Ctrl-Shift-F to reformat the entire file. If any lines are selected when you press Ctrl-Shift-F, only those lines are reformatted.