Develop Reference

Cannot use timestamp in Android Studio(Java), when the button is clicked, Simulator would shout down

long millis = System.currentTimeMillis();
ts.setText((int) millis);
Now trying to show timestamp when "buttonEqual" is clicked, but suddenly it does not work.
I tried to change long -> int and just put millis in side the setText(), but not appropriate.
buttonEqual.setOnClickListener(new View.OnClickListener() {
#RequiresApi(api = Build.VERSION_CODES.N)
#Override
public void onClick(View v) {
if (Addition || Subtract || Multiplication || Division || mRemainder) {
input2 = Float.parseFloat(edt1.getText() + "");
}
if (Addition) {
edt1.setText(input1 + "+" + input2);
Addition = false;
ans.setText(" = " + (input1 + input2) + "");
long millis = System.currentTimeMillis();
ts.setText((int) millis);
}

EditText.setText() expects either a resource id (as int value, specifying a text resource) or a string (with the text to display). Your timestamp is neither.
Assuming that you want to display the timestamp as value, you should write
ts.setText(Long.toString(millis));

Find average/ minimun/maximun

if (cleaningbay >=5)
{
long duration =5;
try
{
System.out.println("\n\t All cleaners are busy..Please wait!..................................................................(-_-)" + bus.getName() );
System.out.println("\n\t" + bus.getName() + "waited for " + duration );
TimeUnit.SECONDS.sleep(duration);
bus.notify();
Cleaners(bus);
bus.wait();
}
catch(InterruptedException iex)
{
iex.printStackTrace();
}
}
else if (cleaningbay < 5)
{
System.out.println("\n\t" + bus.getName() + "is heading to " + bus.getCleanersName() + Clock.get_time());
cleaningbay++;
long duration=0;
try
{
System.out.println("\n\t Cleaning in progress :" + bus.getName() + Clock.get_time() );
duration = (long)(Math.random()* 3);
TimeUnit.SECONDS.sleep(duration);
}
catch(InterruptedException iex)
{
iex.printStackTrace();
}
}
I have these codes in different part of my program where the time is recorded in the variable "duration". I have used the "duration" variable in different methods in the same class. i wanted to know if there is a way of adding of these values "time" and find the avg/min/max

You can define an array to store your times before every time you change the variable, an then use it to calculate your required values.
List<Long> timeHistory = new ArrayList<>();
...
timeHistory.add(duration);
duration = (long)(Math.random()* 3);
timeHistory should be a global variable of your class

If your class gets a lot of traffic, you dont want to store all times in a list, instead I would suggest you create a utility class that help you to keep track of the values you need to get MIN, MAX and AVG, something like this:
public class TimeHistory {
private Long minTime = Long.MAX_VALUE;
private Long maxTime = Long.MIN_VALUE;
private Long timeSum = 0L;
private Long timeCount = 0L;
public void logTime(long time){
if(time < minTime){
minTime = time;
}
if(time > maxTime){
maxTime = time;
}
timeSum += time;
timeCount++;
}
public Long getMinTime() {
return minTime;
}
public Long getMaxTime() {
return maxTime;
}
public Long getTimeAvg() {
return timeSum / timeCount;
}
}
Here you call the method logTime(time); every time you need, and it will take care of keep those values updated for you, then latter you just need to call the methods getMinTime(), getMaxTime() or getTimeAvg().
I hope it helps ;-)

Set int value in conditional statement after declaring string

I have a string (breakmsg) that I would like to be the same for every if statement, with an integer value that needs to change depending on what it is declared as inside the if statement. How would I go about changing the value of the value variable after I have already declared the breakmsg string? Previous attempts are commented inside the code.
Here is my current code:
private int value;
public void setValue(int v){
value = v;
}
#EventHandler
public void onBlockBreak(BlockBreakEvent e) {
Block b = e.getBlock();
Player p = e.getPlayer();
//int value = 0;
String breakmsg = ChatColor.GREEN + "You gained " + ChatColor.GOLD + value + ChatColor.GREEN + " points for collecting " + ChatColor.AQUA + b.getType() + ChatColor.GREEN + ".";
#SuppressWarnings("deprecation")
int itemID = p.getItemInHand().getTypeId();
if (b.getType() == Material.DIAMOND_ORE) {
if (itemID == 257 || itemID == 278) {
//value = 5;
setValue(5);
int points = getConfig().getInt("players." + p.getUniqueId() + ".points");
getConfig().set("players." + p.getUniqueId() + ".points", points + value);
saveConfig();
startScoreboard();
e.getPlayer().sendMessage(breakmsg);
}
}
if (b.getType() == Material.GOLD_ORE) {
if (itemID == 257 || itemID == 285 || itemID == 278) {
//value = 3;
setValue(3);
int points = getConfig().getInt("players." + p.getUniqueId() + ".points");
getConfig().set("players." + p.getUniqueId() + ".points", points + value);
saveConfig();
startScoreboard();
e.getPlayer().sendMessage(breakmsg);
}
}
}

You could wrap that logic in a private function.
private String generateBreakMsgFrom(Block block, int value) {
return ...
}
Then within the if statements rather than setting value you can do:
breakmsg = generateBreakMsgFrom(b, 5);
Please note that you could and should probably also simply set the message after the if statements, but still you want to extract the message generation logic into a private function.
I would really recommend you to read Clean Code. Your function is very long, it is doing multiple things, it has a lot of magic numbers and quite a lot of code duplication...
EDIT: Since you declared int value in your function I haven't realized that it was an instance variable, therefore.
private String generateBreakMsgForBlock(Block block) {
return ... //you can use value from here once properly set
}

System.nanoTime vs System.currentTimeMillis

According to its documentation, System.nanoTime returns
nanoseconds since some fixed but arbitrary origin time. However, on all x64 machines I tried the code below, there were time jumps, moving that fixed origin time around. There may be some flaw in my method to acquire the correct time using an alternative method (here, currentTimeMillis). However, the main purpose of measuring relative times (durations) is negatively affected, too.
I came across this problem trying to measure latencies when comparing different queues to LMAX's Disruptor where I got very negative latencies sometimes. In those cases, start and end timestamps were created by different threads, but the latency was computed after those threads had finished.
My code here takes time using nanoTime, computes the fixed origin in currentTimeMillis time, and compares that origin between calls. And since I must ask a question here: What is wrong with this code? Why does it observe violations of the fixed origin contract? Or does it not?
import java.text.*;
/**
* test coherency between {#link System#currentTimeMillis()} and {#link System#nanoTime()}
*/
public class TimeCoherencyTest {
static final int MAX_THREADS = Math.max( 1, Runtime.getRuntime().availableProcessors() - 1);
static final long RUNTIME_NS = 1000000000L * 100;
static final long BIG_OFFSET_MS = 2;
static long startNanos;
static long firstNanoOrigin;
static {
initNanos();
}
private static void initNanos() {
long millisBefore = System.currentTimeMillis();
long millisAfter;
do {
startNanos = System.nanoTime();
millisAfter = System.currentTimeMillis();
} while ( millisAfter != millisBefore);
firstNanoOrigin = ( long) ( millisAfter - ( startNanos / 1e6));
}
static NumberFormat lnf = DecimalFormat.getNumberInstance();
static {
lnf.setMaximumFractionDigits( 3);
lnf.setGroupingUsed( true);
};
static class TimeCoherency {
long firstOrigin;
long lastOrigin;
long numMismatchToLast = 0;
long numMismatchToFirst = 0;
long numMismatchToFirstBig = 0;
long numChecks = 0;
public TimeCoherency( long firstNanoOrigin) {
firstOrigin = firstNanoOrigin;
lastOrigin = firstOrigin;
}
}
public static void main( String[] args) {
Thread[] threads = new Thread[ MAX_THREADS];
for ( int i = 0; i < MAX_THREADS; i++) {
final int fi = i;
final TimeCoherency tc = new TimeCoherency( firstNanoOrigin);
threads[ i] = new Thread() {
#Override
public void run() {
long start = getNow( tc);
long firstOrigin = tc.lastOrigin; // get the first origin for this thread
System.out.println( "Thread " + fi + " started at " + lnf.format( start) + " ns");
long nruns = 0;
while ( getNow( tc) < RUNTIME_NS) {
nruns++;
}
final long runTimeNS = getNow( tc) - start;
final long originDrift = tc.lastOrigin - firstOrigin;
nruns += 3; // account for start and end call and the one that ends the loop
final long skipped = nruns - tc.numChecks;
System.out.println( "Thread " + fi + " finished after " + lnf.format( nruns) + " runs in " + lnf.format( runTimeNS) + " ns (" + lnf.format( ( double) runTimeNS / nruns) + " ns/call) with"
+ "\n\t" + lnf.format( tc.numMismatchToFirst) + " different from first origin (" + lnf.format( 100.0 * tc.numMismatchToFirst / nruns) + "%)"
+ "\n\t" + lnf.format( tc.numMismatchToLast) + " jumps from last origin (" + lnf.format( 100.0 * tc.numMismatchToLast / nruns) + "%)"
+ "\n\t" + lnf.format( tc.numMismatchToFirstBig) + " different from first origin by more than " + BIG_OFFSET_MS + " ms"
+ " (" + lnf.format( 100.0 * tc.numMismatchToFirstBig / nruns) + "%)"
+ "\n\t" + "total drift: " + lnf.format( originDrift) + " ms, " + lnf.format( skipped) + " skipped (" + lnf.format( 100.0 * skipped / nruns) + " %)");
}};
threads[ i].start();
}
try {
for ( Thread thread : threads) {
thread.join();
}
} catch ( InterruptedException ie) {};
}
public static long getNow( TimeCoherency coherency) {
long millisBefore = System.currentTimeMillis();
long now = System.nanoTime();
if ( coherency != null) {
checkOffset( now, millisBefore, coherency);
}
return now - startNanos;
}
private static void checkOffset( long nanoTime, long millisBefore, TimeCoherency tc) {
long millisAfter = System.currentTimeMillis();
if ( millisBefore != millisAfter) {
// disregard since thread may have slept between calls
return;
}
tc.numChecks++;
long nanoMillis = ( long) ( nanoTime / 1e6);
long nanoOrigin = millisAfter - nanoMillis;
long oldOrigin = tc.lastOrigin;
if ( oldOrigin != nanoOrigin) {
tc.lastOrigin = nanoOrigin;
tc.numMismatchToLast++;
}
if ( tc.firstOrigin != nanoOrigin) {
tc.numMismatchToFirst++;
}
if ( Math.abs( tc.firstOrigin - nanoOrigin) > BIG_OFFSET_MS) {
tc.numMismatchToFirstBig ++;
}
}
}
Now I made some small changes. Basically, I bracket the nanoTime calls between two currentTimeMillis calls to see if the thread has been rescheduled (which should take more than currentTimeMillis resolution). In this case, I disregard the loop cycle. Actually, if we know that nanoTime is sufficiently fast (as on newer architectures like Ivy Bridge), we can bracket in currentTimeMillis with nanoTime.
Now the long >10ms jumps are gone. Instead, we count when we get more than 2ms away from first origin per thread. On the machines I have tested, for a runtime of 100s, there are always close to 200.000 jumps between calls. It is for those cases that I think either currentTimeMillis or nanoTime may be inaccurate.

As has been mentioned, computing a new origin each time means you are subject to error.
// ______ delay _______
// v v
long origin = (long)(System.currentTimeMillis() - System.nanoTime() / 1e6);
// ^
// truncation
If you modify your program so you also compute the origin difference, you'll find out it's very small. About 200ns average I measured which is about right for the time delay.
Using multiplication instead of division (which should be OK without overflow for another couple hundred years) you'll also find that the number of origins computed that fail the equality check is much larger, about 99%. If the reason for error is because of the time delay, they would only pass when the delay happens to be identical to the last one.
A much simpler test is to accumulate elapsed time over some number of subsequent calls to nanoTime and see if it checks out with the first and last calls:
public class SimpleTimeCoherencyTest {
public static void main(String[] args) {
final long anchorNanos = System.nanoTime();
long lastNanoTime = System.nanoTime();
long accumulatedNanos = lastNanoTime - anchorNanos;
long numCallsSinceAnchor = 1L;
for(int i = 0; i < 100; i++) {
TestRun testRun = new TestRun(accumulatedNanos, lastNanoTime);
Thread t = new Thread(testRun);
t.start();
try {
t.join();
} catch(InterruptedException ie) {}
lastNanoTime = testRun.lastNanoTime;
accumulatedNanos = testRun.accumulatedNanos;
numCallsSinceAnchor += testRun.numCallsToNanoTime;
}
System.out.println(numCallsSinceAnchor);
System.out.println(accumulatedNanos);
System.out.println(lastNanoTime - anchorNanos);
}
static class TestRun
implements Runnable {
volatile long accumulatedNanos;
volatile long lastNanoTime;
volatile long numCallsToNanoTime;
TestRun(long acc, long last) {
accumulatedNanos = acc;
lastNanoTime = last;
}
#Override
public void run() {
long lastNanos = lastNanoTime;
long currentNanos;
do {
currentNanos = System.nanoTime();
accumulatedNanos += currentNanos - lastNanos;
lastNanos = currentNanos;
numCallsToNanoTime++;
} while(currentNanos - lastNanoTime <= 100000000L);
lastNanoTime = lastNanos;
}
}
}
That test does indicate the origin is the same (or at least the error is zero-mean).

As far as I know the method System.currentTimeMillis() makes indeed sometimes jumps, dependent on the underlying OS. I have observed this behaviour myself sometimes.
So your code gives me the impression you try to get the offset between System.nanoTime() and System.currentTimeMillis() repeated times. You should rather try to observe this offset by calling System.currentTimeMillis() only once before you can say that System.nanoTimes() causes sometimes jumps.
By the way, I will not pretend that the spec (javadoc describes System.nanoTime() related to some fixed point) is always perfectly implemented. You can look on this discussion where multi-core CPUs or changes of CPU-frequencies can negatively affect the required behaviour of System.nanoTime(). But one thing is sure. System.currentTimeMillis() is far more subject to arbitrary jumps.

Testing code to get the average time for the calls

This is my code, I am trying to test what's the average time to make a call to getLocationIp method by passing ipAddress in that. So what I did is that, I am generating some random ipAddress and passing that to getLocationIp and then calculating the time difference. And then putting that to HashMap with there counts. And after wards I am priniting the hash map to see
what's the actual count. So this is the right way to test this? or there is some other way. Becuase in my case I am not sure whether my generateIPAddress method generates random ipAddress everytime. I am also having start_total time before entering the loop and then end_total time after everything gets completed. So on that I can calculate the average time?
long total = 10000;
long found = 0;
long found_country = 0;
long runs = total;
Map<Long, Long> histgram = new HashMap<Long, Long>();
try {
long start_total = System.nanoTime();
while(runs > 0) {
String ipAddress = generateIPAddress();
long start_time = System.nanoTime();
resp = GeoLocationService.getLocationIp(ipAddress);
long end_time = System.nanoTime();
long difference = (end_time - start_time)/1000000;
Long count = histgram.get(difference);
if (count != null) {
count++;
histgram.put(Long.valueOf(difference), count);
} else {
histgram.put(Long.valueOf(difference), Long.valueOf(1L));
}
runs--;
}
long end_total = System.nanoTime();
long finalTotal = (end_total - start_total)/1000000;
float avg = (float)(finalTotal) / total;
Set<Long> keys = histgram.keySet();
for (Long key : keys) {
Long value = histgram.get(key);
System.out.println("$$$GEO OPTIMIZE SVC MEASUREMENT$$$, HG data, " + key + ":" + value);
}
This is my generateIpAddress method-
private String generateIPAddress() {
Random r = new Random();
String s = r.nextInt(256) + "." + r.nextInt(256) + "." + r.nextInt(256) + "." + r.nextInt(256);
return s;
}
Any suggestions will be appreciated.

Generally when you benchmark functions you want to run the multiple times and average the results That gives you are clearer indication of the actual time your program will spend in them, considering that you rarely care about the performance of something only run once.