The try Block - Java Tutorial 5.0 英文版

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The try Block

The first step in constructing an exception handler is to enclose the code that might throw an exception within a try block. In general, a try block looks like the following.

try {
    code
}
catch and finally blocks . . .

The segment in the example labaled code contains one or more legal lines of code that could throw an exception. (The catch and finally blocks are explained in the next two subsections.)

To construct an exception handler for the writeList method from the ListOfNumbers class, enclose the exception-throwing statements of the writeList method within a try block. There is more than one way to do this. You can put each line of code that might throw an exception within its own try block and provide separate exception handlers for each. Or, you can put all the writeList code within a single try block and associate multiple handlers with it. The following listing uses one try block for the entire method because the code in question is very short.

private Vector victor;
private static final int SIZE = 10;

PrintWriter out = null;

try {
    System.out.println("Entered try statement");
    out = new PrintWriter(new FileWriter("OutFile.txt"));
    for (int i = 0; i < SIZE; i++) {
        out.println("Value at: " + i + " = " 
                     + victor.elementAt(i));
    }
}
catch and finally statements . . .

If an exception occurs within the try block, that exception is handled by an exception handler associated with it. To associate an exception handler with a try block, you must put a catch block after it; the next section shows you how.

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