Java：if条件：使用if内部的变量作为if的条件

Question

As a beginner, I'm trying to code something like that. For sure, the wrong way, because it doesn't work at all. What I'm trying to do is: use the results i can get when I do something inside a if loop and use these results to calculate conditions the next time I enter the if... To be more understanable, I want to do the same thing if cond1 && cond2 are TRUE but not to early even if the situation occurs (delay of 1000) and not at a value under the previous one...

I don't know how to code this, for the first time I enter the if and for the others... Can you help me please??? Thanks a lot.

boolean cond_1 = a < 10;
boolean cond_2 = b < 15;
boolean cond_delay = (time_now - time_i_have_done_something) > 1000;
boolean cond_value = value_now > value_i_have_done_something;

if (cond_A1 == true && cond_A2 == true && cond_delay == true) {
 do something;
 long time_i_have_done_something = do_something.gettime();
 double value_i_have_done_something = do_something.getvalue();
}

Example of the logic I want to implement:

if (cond_A1 == true) { // firt occurence at 7 h 30 min 00 sec 000 ms
time = gettime();
value = getvalue();
IOrder order = engine.submitOrder("EURUSD", instrument, orderCommand, 1); 
}
if (cond_A1 == true) { // second occurence at 7 h 30 min 00 sec 190 ms
// do nothing because time between occurence#1 and occurence#2 < 1000 ms  
}
if (cond_A1 == true) { // firt occurence at 7 h 30 min 01 sec 050 ms
// execute this because time between occurence#1 and occurence#3 > 1000 ms 
time = gettime();
value = getvalue();
IOrder order = engine.submitOrder("EURUSD", instrument, orderCommand, 1); 
}

Answer 1

This will loop, and before the action doSomething() is called, if will check that a condition is true, and that 1 second has passed since the action was last taken. It will also wait for the first action to be taken at a 1 second delay because the first call is not treated as a special case. This can be fixed by declaring start like this:

long start = System.nanoTime() - timeBetween;

I put in a repeat variable with the value of 5. That can of course be removed.

I chose to not sleep() the thread, but just yield() for the processor to be able to take on other tasks while also being able to just busy-loop the program:

import java.time.LocalDateTime;
import java.time.temporal.ChronoUnit;

class StackOverflowTest {

  public static void main(String [] args){
    StackOverflowTest test = new StackOverflowTest();
    test.notTooFast();
  }

  public void notTooFast(){
    boolean condition1  = true;
    long    timeBetween = 1_000_000_000;  // 1 second.
    long    start       = System.nanoTime();
    int     repeat      = 5;              // run the loop only 5 times. 

    while (repeat > 0) {  // or for an endless loop, use: while (true)

      // has timeBetween passed since last time?
      if (condition1 && (System.nanoTime() - start > timeBetween)) {

        start = System.nanoTime(); // reset the time
        doSomething(repeat--);     // don't forget to decrease the counter.

      } else {
        Thread.currentThread().yield();  // hint to yield this threads current use of a processor.
      }
    }
  }

  // just print something for the sake of the example:
  public void doSomething(int countdown){
    System.out.println(LocalDateTime
                         .now()
                         .truncatedTo(ChronoUnit.MILLIS)
                       + ": Doing something "
                       + countdown);
  }
}

It prints:

2020-07-15T13:30:34.409: Doing something 5
2020-07-15T13:30:35.350: Doing something 4
2020-07-15T13:30:36.350: Doing something 3
2020-07-15T13:30:37.349: Doing something 2
2020-07-15T13:30:38.350: Doing something 1

I imagine, the line

doSomething(repeat--);

should probably be replaced with something like this:

repeat--;
IOrder order = engine.submitOrder("EURUSD", instrument, orderCommand, 1);

---

Instead of Thread.currentThread().yield(); , you can also use

try {        
  Thread.currentThread().sleep(1000); // 1 second.
} catch (InterruptedException ex) {
  // handle whichever way
  Thread.currentThread().interrupt();  // reset interrupt flag
}

which will effective put the thread to sleep for 1 second.