println

问题 What is the effect of SYSO - System.out.println() ? If my computer is executing a large job such as fetching 2 Lakhs (approximately 2,000,000) records from a database to a file, does SYSO affect the execution time? 回答1: Of course it affects it. Every operation comes with a cost. Writing to system out is IO, and comes with a non-negligible cost. To know the exact effect on your program, there's no other solution than benchmarking: run the program with and without the println calls, and measure

问题 When logging-out a float in Objective-C you can do the following to limit your output to only 2 decimal places: float avgTemp = 66.844322156 NSLog (@"average temp. = %.2f", avgTemp); But how do you do this in Swift? And how do you escape other characters in println in Swift? Here's a regular Swift println statement: println ("Avg. temp = \(avgTemp)") So how do you limit decimal places? Also, how do you escape double-quotes in println ? 回答1: Here's the shortest solution I found thus far: let

问题 I make a brand new grails project and put this in the bootstrap: ExpandoMetaClass.enableGlobally() Integer.metaClass.precision = {->return 1} println 3.precision() println "rofl" println 15.precision() And it does what I expect, run-app prints: 1 rofl 1 But if i take out the println "rofl" it won't print that second one. It just prints one 1 without the rofl... WTF? Again, becasue this doesn't make any sense to me, this code: ExpandoMetaClass.enableGlobally() Integer.metaClass.precision = {-

问题 class Test { int a = 100; System.out.println(a); } class Demo { public static void main(String args[]) { Test t = new Test(); } } I'm new to programming. I found this code when I'm practicing. I don't understand why I'm getting this error. Here is the error I'm getting. Demo.java:3: error: <identifier> expected System.out.println(a); ^ Demo.java:3: error: <identifier> expected System.out.println(a); ^ 2 errors Compilation failed. Can you guys explain why I'm getting this error? 回答1: You can't

问题 I am trying to get a pop-up message when the cake node is clicked on. It prints to the console, but "JOptionPane.showMessageDialog(null,"Test");" crashes the program when I click on the cake (no errors). Any ideas? class Cake extends Item { double dx=3,dy=1.6; Cake(String imageFile, double x, double y) { super(imageFile, x, y); } @Override public void move() { this.setX(this.getX()+dx); if(this.getX()>749 || this.getX()<-20) { dx=-dx; } this.setY(this.getY()+dy); if(this.getY()>530 || this

问题 I am a beginner in Java and I have a run time error question. I have answered it correctly, however I do not completely understand the concept behind the answer. Could someone please explain why B is the right answer to the question, thank you: Consider the following declarations: private ArrayList<String> list; ... public void printAll() { int index = 0; while (index < list.size) { index = index + 1; System.out.println(list.get(index)); } } Assuming that list is not null, which one of the

问题 I modified some code I found to display a local variable instead of set text inside of a JFrame, but I'm unable to find a way to change the size of the text. I keep reading about frameName.setFont(new Font(____)), but that doesn't seem to be working for the println. How would I modify the text size? Here's my current code. (P.S. I'm new, so I'm sorry that i don't know what I'm talking about.) import java.util.*; import java.io.*; import java.awt.*; import javax.swing.*; import java.time.*;

问题 I want to create a function in C++ using cout that has the same as the println function in java. This means that the call should be something like this: int a=5 println("A string" + a); the variable a should have any basic type. What kind of parameter should I have in this case and how would it work? Thanks 回答1: As larsmans already pointed out, java has overloads on the operator +. So you can concat strings with integer. This is also possible in C++ but not out of the box for all types. You

问题 Is there any way in Java that you can make a println appear only when requested, not by default? Basically something similar to using "-v" in many programs to give you verbose mode, with information on what is happening. For example let's say I have an if statement in a loop, and a simple println that tells me whether the if statement evaluates to true for each iteration of the loop. Is there any other way to toggle on/off it's visibility other than commenting it out when I don't need it and

问题 Can somebody explain me why this code does not print the numbers? String text = new String("SomeString"); for (int i=0; i<1500; i++) { text = text.concat(i+""); } System.out.println(text); Result SomeString If I lower the number of runs to 1000 it works, why?! And also if I add not only a number but also a character, it works. Ok New Update: Thanks for the code examples. I tried them all but what I found out is, that the console actually display the numbers but only in fontcolor white. But