如何将double转换为2位小数？

Question

这是代码：如何让它只显示小数点后两位？ 当我使用String.format("%.2f", maltRequiredString);时，我的应用程序崩溃String.format("%.2f", maltRequiredString);

public class MainActivity extends AppCompatActivity {

    EditText batchVolEditText;
    EditText ogEditText;
    EditText bheEditText;
    TextView maltRequiredTextView;


    public void calculate(View view) {

        String batchVolString = batchVolEditText.getText().toString();
        String ogString = ogEditText.getText().toString();
        String bheString = bheEditText.getText().toString();

        double batchVolDouble = Double.parseDouble(batchVolString);
        double ogDouble = Double.parseDouble(ogString);
        double bheDouble = Double.parseDouble(bheString);
        double specificGravity = 0.96;

        double maltRequired = (batchVolDouble * ogDouble * specificGravity) / bheDouble;


        String maltRequiredString = Double.toString(maltRequired);

        maltRequiredTextView.setText(maltRequiredString + "kg");


    }

Answer 1

记住你不能使用

 String.format("%.2f", maltRequiredString);

因为 maltRequiredString 是字符串。 正确的编码是您必须在此函数中使用 float，为此您必须将字符串转换为 float

float f = Float.valueOf(maltRequiredString);  
String test = String.format("%.02f", f);

您也可以使用此技术将其设为 2 位小数

DecimalFormat decimalFormat = new DecimalFormat("#.##");
float twoDigitsF = Float.valueOf(decimalFormat.format(f));

Answer 2

您可以使用 DecimalFormat 来克服这个问题。

//Make a new instance df that has 2 decimal places pattern.
Decimalformat df = new DecimalFormat("#.##");

// converting maltRequired form double to string.
String maltRequiredString  = df.format(maltRequired);

// then set the value of maltRequiredString to the TextView.
maltRequiredTextView.setText(String.valueOf(maltRequiredString));