Question

我有以下转换方案守则:

private void convertButtonActionPerformed(java.awt.event.ActionEvent evt) {

    int type, value;
    double conversion;
    String output;

    type = Integer.parseInt(conversionchoiceInput.getText());
    value = Integer.parseInt(valueInput.getText());

    if (type == 1)
    {
    conversion = inchesToCentimetres(value);
    output = value + " inches = " + Math.round(conversion) + " centimetres";
    }
    else if (type == 2)
    {

    }
    else if (type == 3)
    {

    }
    else if (type == 4)
    {

    }
    outputLabel.setText(output); 
}

它说,如果我已经知道,“可变的产出可能不会被启动”?

感谢!

Answer 1

问题是,无论方案执行方式如何,都必须首先采用<代码>产出。只是在<代码>if的道路上启动。因此,你必须从一开始就给它一个缺省值(空洞或某种东西),或将其归入所有分支机构。

String output = "";

或

if (type == 1)
{
    conversion = inchesToCentimetres(value);
    output = value + " inches = " + Math.round(conversion) + " centimetres";
}
else if (type == 2)
{
    output = "";
}
else if (type == 3)
{
    output = "";
}
else if (type == 4)
{
    output = "";
}

自然,第一个选择是最好的。

Answer 2

If type != 1, then output isn t initialized. And even if you give output a value in each of the if branches (1, 2, 3, 4) output might not have been initialized, as if type < 1 or > 4 it still has no value.

Answer 3

你刚刚宣布,那里的变化不同于最初的变数。

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