问题描述
我写了创建一个包含3阵列报表对象小班。在创建对象的这些阵列被初始化用的值。然而，当我测试类，例如，见有什么部门数组中，它打印出的数组元素都为null。为什么？
I wrote a small class that creates a report object containing 3 arrays. At creation of the object these arrays are initialised with values. However when i test the class to see for example what's in the departments array, it prints out that the array elements are null. why?
class Report
{
// declare instance variables (arrays)
public String[] departments = new String[4] ;
public double[] grossTotals = new double[4] ;
public double[] taxTotals = new double[4] ;
// constructor
public Report(){
// declare, create and initialise all in one statement
String[] departments = {"Accounting", "Sales", "HR", +
"Administration"} ;
double[] grossTotals = {0.0, 0.0, 0.0, 0.0} ;
double[] taxTotals = {0.0, 0.0, 0.0, 0.0} ;
} // END constructor
} // class Report
测试类：
class TestReport
{
public static void main(String[] args) {
// create report object
Report r = new Report();
for (int i = 0; i <= 3 ; i++ )
{
System.out.println(r.departments[i]) ;
}
} //end main
} // end test class
感谢
巴巴
推荐答案
请像这样
public Report(){
// declare, create and initialise all in one statement
this.departments = {"Accounting", "Sales", "HR", +
"Administration"} ;
this.grossTotals = {0.0, 0.0, 0.0, 0.0} ;
this.taxTotals = {0.0, 0.0, 0.0, 0.0} ;
} // END constru
其实你正在创造新的数组对象，您的本地构造那些构造越来越初始化。
Actually you are creating new arrays objects local to your constructor those are getting initialized in constructor.
你的类字段会使用上述code被初始化。
your class fields will be initialized using the code above .
**
：**
上述code会给你前pression的非法启动
:**Above code will give you illegal start of expression
下面是工作code
class Report
{
// declare instance variables (arrays)
public String[] departments = null;
public double[] grossTotals = null;
public double[] taxTotals = null;
// constructor
public Report(){
this.departments = new String[]{"Accounting", "Sales", "HR", "Administration"} ;
this.grossTotals = new double[]{0.0, 0.0, 0.0, 0.0} ;
this.taxTotals = new double[]{0.0, 0.0, 0.0, 0.0} ;
} // END constructor
}
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