Figure 9-5: The Delegate Methods Generation dialog in Java

Generation Quick Response Code in Java Figure 9-5: The Delegate Methods Generation dialog

Eclipse s Source menu gives you two ways to create constructors When you choose Source Generate Constructor Using Fields, Eclipse gives values to the subclass s fields When you choose Source Add Constructor from Superclass, Eclipse gives values to the parent class s fields Figure 9-7 illustrates the point The Generate Constructor Using Fields action uses assignment statements; the Add Constructor action passes parameters Both actions call the parent class s constructor So, in some situations, both actions give you the same result

For a concrete example, look over the code in Listing 9-1

Listing 9-1:

class Employee { private String name; private String jobTitle; public Employee() { super(); }

public Employee(String name, String jobTitle) { super(); thisname = name; thisjobTitle = jobTitle; } Etc (No additional constructors) } class PartTimeEmployee extends Employee { private double hourlyRate; Etc (No constructors) }

If I choose Source Generate Constructor Using Fields with the PartTimeEmployee class in the editor, I see the dialog in Figure 9-8 This dialog creates one constructor To create two constructors, I have to choose Generate Constructor Using Fields twice

I use this dialog in Figure 9-8 twice once with hourlyRate unchecked, and a second time with hourlyRate checked When the dust settles, I have the code shown in Figure 9-9

Some people have strange notions of what it means to have fun Just for fun, I wiped the slate clean I deleted the code that I created using Generate

Constructor, and I returned to the pristine code in Listing 9-1 Then I do it all again But this time around, I choose Source Add Constructor from Superclass As a result, I see the dialog in Figure 9-10

If I put check marks in both of Figure 9-10 s boxes, I get the constructors shown in Figure 9-11 One constructor is the same as a constructor created by the Generate Constructor Using Fields action The other constructor is unique to the Add Constructor from Superclass action

A try/catch block is like a safety net If anything goes wrong inside the block, your program can recover gracefully Choosing Source Surround with try/catch Block is like applying the try template But the Surround with try/catch Block action is much smarter than the try template To find out more about the try template, see 7 To see how smart the Surround with try/catch Block action is, march over to the editor and select the following lines of code:

FileInputStream stream = new FileInputStream( myData ); Threadsleep(2000);

Then choose Source Surround with try/catch Block When you do all this, you get the following result:

import javaioFileNotFoundException; try { FileInputStream stream = new FileInputStream( myData ); Threadsleep(2000); } catch (FileNotFoundException e) { // TODO Auto-generated catch block eprintStackTrace(); } catch (InterruptedException e) { // TODO Auto-generated catch block eprintStackTrace(); }

Eclipse even adds the import declaration for the FileNotFoundException If you apply the try template to the same code, you get the following wishywashy result:

try { FileInputStream stream = new FileInputStream( myData ); Threadsleep(2000); } catch (Exception e) { // TODO: handle exception }

It gets even better If you apply Surround with try/catch Block to code that contains a super call, Eclipse answers back with a message: Cannot surround a super constructor call (How about that! Eclipse knows that you re not allowed to put a super call inside a try/catch block!) What if you apply the Surround with try/catch Block action to the following code

fib = previous + prePrevious; prePrevious = previous; previous = fib; Systemoutprintln(fib);

The code doesn t throw any checked exceptions, so Eclipse asks you if really need a try/catch block (See Figure 9-12)