refresh files structure for java source
	new file:   ch02/2.6/java_src/Scan.java
	renamed:    ch02/2.6/java_src/Lexer.java -> ch02/2.6/java_src/lexer/Lexer.java
	renamed:    ch02/2.6/java_src/Num.java -> ch02/2.6/java_src/lexer/Num.java
	renamed:    ch02/2.6/java_src/Tag.java -> ch02/2.6/java_src/lexer/Tag.java
	renamed:    ch02/2.6/java_src/Token.java -> ch02/2.6/java_src/lexer/Token.java
	renamed:    ch02/2.6/java_src/Word.java -> ch02/2.6/java_src/lexer/Word.java
	renamed:    ch02/2.6/java_src/makefile -> ch02/2.6/java_src/lexer/makefile