double in Java example for Android development
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Java double is 64 bit double precision type used when fractional
precision calculation is required.
Java double je datový typ (reálné číslo) o velikosti 64 bitů. Používá se například pro přesný výsledek po dělení za desetinnou tečkou. Pokud nepotřebuje tak veliké číslo použijte raději typ float, šetříte tím paměť mobilního telefonu.
precision calculation is required.
Java double je datový typ (reálné číslo) o velikosti 64 bitů. Používá se například pro přesný výsledek po dělení za desetinnou tečkou. Pokud nepotřebuje tak veliké číslo použijte raději typ float, šetříte tím paměť mobilního telefonu.
// declaration and assignment of value type double
double x = 18.41785;
//print formated value
System.out.printf("The value of x is %.3f%n", x); // 18.418
// declaring more variables in single statement
double d1 = 12.4, d2 = 564.5, d3 = 14.589;
// double range of value
System.out.println(Double.MIN_VALUE); // 4.9E-324
System.out.println(Double.MAX_VALUE); // 1.7976931348623157E308
// is NaN Not-a-Number
double f = (double) Math.sqrt(-15);
boolean bNaN = Double.isNaN(f);
System.out.print(bNaN); // true
// check if a string is a valid number in Java example
// convert string to double Java example
String sD = "12.8";
double dParse = Double.parseDouble(sD);
// convert strings to numbers
String sDl = "15.48";
double dFromString = (Double.valueOf(sDl)).doubleValue();
// format double, float or long value to string
DecimalFormat formatter = new DecimalFormat(".##");
String s = formatter.format(-.5678); // -0.57
// .### -0.568
// .#### -0.5678
// .000000 -.567800
// -123.456
// .## -123.46
// #.## -123.46
// #E0 -.1E3
// ##E0 -1.2E2
//###E0 -123E0
// double to string in Java example code
Double dObj = new Double(68.5);
String str = dObj.toString();
// else
Double dS = 11.6;
String sdouble = dS.toString();
// compare two double variables
Double dComp1 = 4.3;
if(dComp1.equals(4.3))
System.out.print("true");
// compares the two specified double values in Java example
// int i = compare(double d1, double d2);
int i = Double.compare(11.5, 11.7); // -1 first < second
// 0 first == second
// 1 first > second
System.out.print(i);
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GregorianCalendar cal = new GregorianCalendar(); Boolean b = cal.isLeapYear(2012); // true, Android example.
public class MainActivity extends Activity {
TextView txtV;
Context cntx;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
txtV = (TextView)findViewById(R.id.idLabel);
cntx = this;
StringBuilder strBuild = new StringBuilder();
GregorianCalendar cal = new GregorianCalendar();
Boolean b = cal.isLeapYear(2012); // true
strBuild.append("Is leap year 2012? " + b + "
");
b = cal.isLeapYear(2014); // false
strBuild.append("Is leap year 2014? " + b + "
");
txtV.setText(strBuild);
}
}
drawPath, canvas.rotate, lineTo basic Android example for your testing.
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// //www.apache.org/licenses/LICENSE-2.0
// The Android Open Source Project
public class MainActivity extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(new SampleView(this));
}
private static class SampleView extends View {
private Paint mPaint = new Paint();
private Path mPath = new Path();
// CONSTRUCTOR
public SampleView(Context context) {
super(context);
setFocusable(true);
// Construct a wedge-shaped path
mPath.moveTo(0, -60);
mPath.lineTo(-20, 80);
mPath.lineTo(0, 60);
mPath.lineTo(20, 80);
mPath.close();
}
@Override
protected void onDraw(Canvas canvas) {
Paint paint = mPaint;
canvas.drawColor(Color.WHITE);
paint.setAntiAlias(true);
paint.setColor(Color.RED);
paint.setStyle(Paint.Style.FILL);
Bitmap bitmapOrg = BitmapFactory.decodeResource(getResources(),
R.drawable.flower_blue);
canvas.drawBitmap(bitmapOrg, 10, 10, paint);
int w = canvas.getWidth();
int h = canvas.getHeight();
int cx = w / 2;
int cy = h / 2;
canvas.translate(cx, cy);
// uncomment next line
//canvas.rotate(90.0f);
canvas.drawPath(mPath, mPaint);
}
}
}
For some graphics you can use Paint.NET editor.
//www.getpaint.net/
How create Snow Effects on Text by 1 minute show this video:
//www.getpaint.net/
How create Snow Effects on Text by 1 minute show this video:
If on Android emulator home button pressed.
Diagram of Activity lifecycle if button HOME pressed
// button home presssed
19:37:06.727: INFO/ActivityManager(60): Starting:
Intent { act=android.intent.action.MAIN cat=[android.intent.category.HOME]
flg=0x10200000 cmp=com.android.launcher/com.android.launcher2.Launcher } from pid 60
19:37:06.807: INFO/onSaveInstanceState(339): onSaveInstanceState()
19:37:06.848: INFO/onPause(339): onPause()
19:37:07.968: INFO/onStop(339): onStop()
Diagram of Activity lifecycle if button HOME pressed
If you create a button or view programmatically with OnClickListener you can set a tag key before button in parent layout is added.
And get correct button by this tag getTag() instead getId() in OnClickListener etc.
And get correct button by this tag getTag() instead getId() in OnClickListener etc.
Button button = new Button(getApplicationContext());
int idOfButton = button.getId(); // return -1
button.setTag("my_button");
String sTag = (String) button.getTag(); // return "my_button"
Editace: 2011-09-26 20:49:42
Počet článků v kategorii: 397
Url:double-in-java-example-for-android-development
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