This reference is for Processing 3.0+. If you have a previous version, use the reference included with your software in the Help menu. If you see any errors or have suggestions, please let us know. If you prefer a more technical reference, visit the Processing Core Javadoc and Libraries Javadoc.



BufferedReader reader;
String line;
void setup() {
  // Open the file from the createWriter() example
  reader = createReader("positions.txt");    
void draw() {
  try {
    line = reader.readLine();
  } catch (IOException e) {
    line = null;
  if (line == null) {
    // Stop reading because of an error or file is empty
  } else {
    String[] pieces = split(line, TAB);
    int x = int(pieces[0]);
    int y = int(pieces[1]);
    point(x, y);
Description The catch keyword is used with try to handle exceptions. Sun's Java documentation defines an exception as "an event, which occurs during the execution of a program, that disrupts the normal flow of the program's instructions." This could be, for example, an error while a file is read.
try {
} catch (exception) {
tryStatements if this code throws an exception, then the code in "catch" is run
exception the Java exception that was thrown
catchStatements code that handles the exception
Updated on January 1, 2021 03:38:12am EST