java/examples/Basics/Data/VariableScope/applet/VariableScope.java

@@ -0,0 +1,81 @@
+import processing.core.*; 
+
+import java.applet.*; 
+import java.awt.*; 
+import java.awt.image.*; 
+import java.awt.event.*; 
+import java.io.*; 
+import java.net.*; 
+import java.text.*; 
+import java.util.*; 
+import java.util.zip.*; 
+import java.util.regex.*; 
+
+public class VariableScope extends PApplet {
+
+/**
+ * Variable Scope. 
+ * 
+ * Variables may either have a global or local "scope". 
+ * For example, variables declared within either the
+ * setup() or loop() functions may be only used in these
+ * functions. Global variables, variables declared outside
+ * of setup() and loop(), may be used anywhere within the program.
+ * If a local variable is declared with the same name as a
+ * global variable, the program will use the local variable to make 
+ * its calculations within the current scope. Variables may be localized
+ * within classes, functions, and iterative statements. 
+ */
+ 
+int a = 20;  // Create a global variable "a"
+
+public void setup() 
+{
+  size(200, 200);
+  background(51);
+  stroke(255);
+  noLoop();
+}
+
+public void draw()
+{
+  // Draw a line using the global variable "a"
+  line(a, 0, a, height);
+  
+  // Create a new variable "a" local to the for() statement 
+  for(int a=50; a<80; a += 2) {
+    line(a, 0, a, height);
+  }
+  
+  // Create a new variable "a" local to the loop() method
+  int a = 100;
+  // Draw a line using the new local variable "a"
+  line(a, 0, a, height);  
+  
+  // Make a call to the custom function drawAnotherLine()
+  drawAnotherLine();
+  
+  // Make a call to the custom function setYetAnotherLine()
+  drawYetAnotherLine();
+}
+
+public void drawAnotherLine() 
+{
+  // Create a new variable "a" local to this method
+  int a = 185;
+  // Draw a line using the local variable "a"
+  line(a, 0, a, height);
+}
+
+public void drawYetAnotherLine() 
+{
+  // Because no new local variable "a" is set, 
+  // this lines draws using the original global
+  // variable "a" which is set to the value 20.
+  line(a+2, 0, a+2, height);
+}
+
+  static public void main(String args[]) {
+    PApplet.main(new String[] { "VariableScope" });
+  }
+}