Java writing to stdout

How to write/print text to the console (stdout) in Java

Or use an existing parser library to read CSV files, JSON files, XML files and so on.) So to read text from a file (or standard input) in production code, you would typically do something like this: or and then use the various methods to either read lines or individual items.

How to write/print text to the console (stdout) in Java

I want to print something to the console, similar to console.log in JavaScript, puts in Ruby, println in Kotlin, etc.

But Java doesn’t have top-level functions or any obvious console-related classes in the standard library. What class or method do I use to simply write text to the console (stdout)?

If you want to print text to the console with a newline at the end, you can use System.out.println , like so:

System.out.println("text here"); 

If you are familiar with C, this is equivalent to puts(«text here»); .

If you want to print text without a newline character at the end, you can use System.out.print :

System.out.print("Hello, "); System.out.println("world!"); 

Note that the two strings appear on the same line, despite being printed separately.

If you are familiar with C, this is equivalent to fputs(«text here», stdout); and/or printf(«text here»);

You can also substitute System.out with System.err in either of the above two commands to write to stderr instead of stdout. In the typical case, both streams will appear in the console, but they can be separately redirected using the appropriate OS-specific commands when running your Java application.

JNI Java from C++, Im using JNI to call some Java code in a C++ program. I need to print some text from Java to C++ stdout. How can I do it? I try: System.out.println(«sdf»); in java, nothing appears. Please , help :D. java c++ java-native-interface stdout. Share. Improve this question. Follow asked Oct 23, 2013 at 17:09.

How does StdIn/Out in Java work?

Im new to Java and am trying to make a QuickUnion algorithm run. I have these text files on my desktop and want to program to read the integers in them. This is the end of the QuickUnion class.

 public static void main(String[] args) < int N = StdIn.readInt(); // Read number of sites QuickUnionUF quickunion = new QuickUnionUF(N); while (!StdIn.isEmpty()) < int p = StdIn.readInt(); int q = StdIn.readInt(); // Read pair to connect if (quickunion.connected(p, q)) continue; // Ignore if connected quickunion.union(p, q); // Combine components StdOut.println(p + " " + q); // and print connection >StdOut.println(quickunion.count() + " components"); > 

My question is: how does StdIn work? How do I read the text file? the first test file contains two columns of numbers.

The Std library does not provide the functionality that is needed to read from an arbitrary file. Its purpose is to provide an easy way for beginners (students) to write simple programs that read and write to standard input / standard output. It has limited functionality 1 .

By contrast, production code uses the standard System.in and System.out , either directly or (in the case of System.in ) via the Scanner class. So to read text from a file (or standard input) in production code, you would typically do something like this:

Scanner in = new Scanner(new File("/some/path/to/file.txt")); 

Scanner in = new Scanner(System.in); 

and then use the various Scanner methods to either read lines or individual items.

(You could also use the Reader or BufferedReader APIs, and parse the input lines yourself in various ways. Or use an existing parser library to read CSV files, JSON files, XML files and so on.)

Your example would look something like this:

import java.util.Scanner; . public static void main(String[] args) < Scanner in = new Scanner(System.in); // replace as required! int n = in.nextInt(); // Read number of sites QuickUnionUF quickUnion = new QuickUnionUF(n); while (in.hasNextInt()) < int p = in.nextInt(); int q = in.nextInt(); // Read pair to connect if (quickUnion.connected(p, q)) continue; // Ignore if connected quickUnion.union(p, q); // Combine components System.out.println(p + " " + q); // and print connection >System.out.println(quickUnion.count() + " components"); > 

Note that new Scanner(new File(someString)) is declared as throwing FileNotFoundException which your code must deal with.

1 — My advice would be to stop using StdIn , StdOut and the rest as soon as you can. Learn to use the standard APIs, and switch.

Standard library (Std) is often provided for students who are taking their first course in programming in Java. Std library is not part of «installed java libraries» therefore in order to use it you have to download the Std library and declare it in your path. It works identical to Java Scanner Class. Consider

public static void main(String[] args) < StdOut.print("Type an int: "); int a = StdIn.readInt(); StdOut.println("Your int was: " + a); StdOut.println(); >> 

Which takes in only ONE integer, a , and prints it out. How ever as I see you’re using isEmpty() which returns true if standard input is empty (except possibly for whitespace). Therefore you can use the isEmpty() to take in as many input as you want. Here is an example code of this usage

public static void main(String[] args) < double sum = 0.0; // cumulative total int n = 0; // number of values while (!StdIn.isEmpty()) < double x = StdIn.readDouble(); sum = sum + x; n++; >StdOut.println(sum / n); > 

Which calculates instantly the average of your inputs and prints it out as you type in new input.

How to print to stderr and stdout in Python?, Last Updated : 27 May, 2021. In Python, whenever we use print () the text is written to Python’s sys.stdout, whenever input () is used, it comes from sys.stdin, and whenever exceptions occur it is written to sys.stderr. We can redirect the output of our code to a file other than stdout.

How to print raw byte content from a byte[] array to stdout in Java?

I am doing the same project as describe here:

Wrap deflated data in gzip format

My problem is that when I try to print out bytes, I get weird results. My problems occur in the following code(Sorry for my bad choice of variables):

 for(int k = 0; k < head.length; k++)< System.out.write(head[k]); >for(int m = 0; m < a.size(); m++)< int comprlength = a.get(m).getclength(); for(int ii = 0; ii < comprlength; ii++)< System.out.write(a.get(m).getcompr()[ii]); >> for(int j = 0; j < f1.length; j++)< System.out.write(f1[j]); >for(int ll = 0; ll

The last two for-loops do not print out the contents of the their byte arrays. Thus I get a unexpected end of file error when using gzip. The weird thing is that if I comment out the second for-loop block (the block with the variables m and ii), nothing gets printed out.

So how do I properly print out the contents of my byte arrays? Why does the first for-loop print out properly when the second for-loop is not commented and why does it not print anything if that second for-loop is commented?

I want to write out the raw bytes. And I want to do it so that it is right after each other for every one of my byte arrays

Assuming your byte array is called buf :

 System.out.println(Arrays.toString(buf)); 

Edit: It sounds like what you really want to do is write your bytes to stdout, not print them. See http://docs.oracle.com/javase/6/docs/api/java/io/PrintStream.html for the difference between printing to a stream and writing to it. Easiest way should be to call the write(byte[] b) method:

 /* There is an image / ic_launcher in the drawable folder for which I am making ByteArray */ Bitmap bmp = BitmapFactory.decodeResource(getResources(), R.drawable.img); ByteArrayOutputStream stream = new ByteArrayOutputStream(); bmp.compress(Bitmap.CompressFormat.PNG, 100, stream); byte[] mByteArray = stream.toByteArray(); 

/* here I am showing the raw data not in hexadecimal format */

 System.out.println(Arrays.toString(mByteArray)); 

I think this will help you guys!

Java — How do I print to the stdout when a gradle build, 1. If you look into the setup in this article you can see you can log to gradle output via System.out.println () – Arthur Klezovich. Nov 9, 2021 at 21:15. @MichałKrzywański Yes! That’s the flag I’m looking for, thank you! – ergonaut. Nov 9, 2021 at 21:26.

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Working of StdOut in Java

This tutorial describes the StdOut class and demonstrates the working of StdOut in Java.

StdOut in Java

The StdOut class is used to print the standard output. This class provides methods to print numbers and strings to standard output. The StdOut class must be in the classpath if we want to use it in our code.

Most of the time, the class is included in the auto-installer, and if it is not, the jar file for StdOut can be downloaded and added to the classpath . We can also add the StdOut.Java in the workplace.

Here is a simple example for StdOut in Java:

package delftstack;  public class Example   public static void main(String[] args)   int Number1 = 14;  int Number2 = 277;  int Number3 = 126;  int Calculation = Number1 + Number2 - Number3;  StdOut.println("Hello, This is delftstack.com");  StdOut.printf("%d + %d - %d = %d\n", Number1, Number2, Number3, Calculation);  > > 

The code above uses StdOut.println and StdOut.printf methods to print the standard outputs. The printf method takes parameters that will be printed in a standard way. See the following result.

Hello, This is delftstack.com 14 + 277 - 126 = 165 

• The behaviour of System.out and StdOut is the same, but StdOut has a few technical differences.
• The StdOut will flush the output, and the outcome will immediately be seen in the terminal.
• The StdOut forces the character encoding to UTF-8 to make it standard.
• The StdOut forces the locale to Locale.US for consistency and floating point values.

Sheeraz is a Doctorate fellow in Computer Science at Northwestern Polytechnical University, Xian, China. He has 7 years of Software Development experience in AI, Web, Database, and Desktop technologies. He writes tutorials in Java, PHP, Python, GoLang, R, etc., to help beginners learn the field of Computer Science.

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Java writing to stdout

Overview. The StdOut class provides methods for printing strings and numbers to standard output. Getting started. To use this class, you must have StdOut.class in your Java classpath. If you used our autoinstaller, you should be all set. Otherwise, either download stdlib.jar and add to your Java classpath or download StdOut.java and put a copy in your working directory. Here is an example program that uses StdOut :

• StdOut coerces the character-set encoding to UTF-8, which is a standard character encoding for Unicode.
• StdOut coerces the locale to Locale.US , for consistency with StdIn , Double.parseDouble(String) , and floating-point literals.
• StdOut flushes standard output after each call to print() so that text will appear immediately in the terminal.

Method Summary

Prints a formatted string to standard output, using the specified format string and arguments, and then flushes standard output.

Prints a formatted string to standard output, using the locale and the specified format string and arguments; then flushes standard output.

Methods inherited from class java.lang.Object

Method Detail

println

public static void println()

println

println

public static void println​(boolean x)

println

public static void println​(char x)

println

public static void println​(double x)

println

public static void println​(float x)

println

public static void println​(int x)

println

public static void println​(long x)

println

public static void println​(short x)

println

public static void println​(byte x)

Prints a byte to standard output and then terminates the line. To write binary data, see BinaryStdOut .

print

print

print

public static void print​(boolean x)

print

public static void print​(char x)

print

public static void print​(double x)

print

public static void print​(float x)

print

public static void print​(int x)

print

public static void print​(long x)

print

public static void print​(short x)

print

public static void print​(byte x)

printf

Prints a formatted string to standard output, using the specified format string and arguments, and then flushes standard output.

printf

public static void printf​(Locale locale, String format, Object. args)

Prints a formatted string to standard output, using the locale and the specified format string and arguments; then flushes standard output.

main

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