Generate key use Math.random correctly or precisely random

zhourenjian@gmail.com · zhourenjian@gmail.com · commit bd204676cd6a · 2014-03-11T12:41:21.000Z
diff --git a/sources/net.sf.j2s.ajax/ajaxpipe/net/sf/j2s/ajax/CompoundPipeRunnable.java b/sources/net.sf.j2s.ajax/ajaxpipe/net/sf/j2s/ajax/CompoundPipeRunnable.java
@@ -3,13 +3,12 @@
 public class CompoundPipeRunnable extends SimplePipeRunnable {
 	
 	private static String nextSessionKey() {
-		String hexStr = "0123456789abcdef";
-		String key = "";
+		StringBuffer keyBuffer = new StringBuffer(4);
 		for (int i = 0; i < 4; i++) {
-			int hex = (int) Math.round(15 * Math.random());
-			key += "" + hexStr.charAt(hex);
+			int hex = (int) Math.floor(Math.random() * 16);
+			keyBuffer.append((char) (hex < 10 ? ('0' + hex) : ('a' + hex - 10)));
 		}
-		return key;
+		return keyBuffer.toString();
 	}
 	
 	CompoundPipeSession[] pipes;
diff --git a/sources/net.sf.j2s.ajax/ajaxpipe/net/sf/j2s/ajax/SimplePipeHelper.java b/sources/net.sf.j2s.ajax/ajaxpipe/net/sf/j2s/ajax/SimplePipeHelper.java
@@ -120,7 +120,7 @@ synchronized static String registerPipe(SimplePipeRunnable pipe) {
 	static String nextPipeKey() {
 		StringBuffer buf = new StringBuffer(SimplePipeRequest.PIPE_KEY_LENGTH);
 		for (int i = 0; i < SimplePipeRequest.PIPE_KEY_LENGTH; i++) {
-			int r = (int) Math.round((float) Math.random() * 61); // 0..61, total 62 numbers
+			int r = (int) Math.floor(Math.random() * 62); // 0..61, total 62 numbers
 			if (r < 10) {
 				buf.append((char) (r + '0'));
 			} else if (r < 10 + 26) {
