Java 天地·Core Java·Lecture Notes·Unitt5 - Array and Strings

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Common declaration and definition errors

Two common errors (though easily spotted and debugged) as:

having a different type when declaring and defining an array
forgetting the double square brackets "[" "]" when declaring or defining an array

The of these problems is illustrated with the example applet ArrayDefinition below: import java.applet.Applet;

class ArrayDefinition extends Applet
{
double monthlySales[];

public void init()
{

monthlySales = new int[12]; }
} When compiled, this applet results in the following output:

The error in this case is that the array monthlySales has been declared as an array of type double, but when its dimension (size ) 12 is defined, the variable type int has been written by mistake.

The second common error, forgetting the open and closed square brackets is illustrated in the program below:

import java.applet.Applet;

class ArrayDeclaration extends Applet
{
double dailyCosts;

public void init()
{

dailyCosts = new double[31]; }
} The result of trying to compile this program is as follows:

The error in this case is that when declared, the programmer forget to include the double square brackets. The line:

double dailyCosts;

is valid, but does not declare dailyCosts to be an identifier of an array of double variables ?it simply declares dailyCosts to be the identifier of a one double variable.

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