流式输入/输出 示例
/*
wc( )方法对任何输入流进行操作并且计算字符数，行数和字数。它在lastNotWhite里追踪字数的奇偶和空格。当在没有参数的情况下执行时，WordCount以System.in为源流生成一个InputStreamReader对象。该流然后被传递到实际计数的 wc( )方法。当在有一个或多个参数的情况下执行时，WordCount 假设这些文件名存在并给每一个文件创建FileReader，传递保存结果的FileReader对象给wc( ) 方法。两种情况下，在退出之前都打印结果。
*/
//A word counting utility.
import java.io.*;
class WordCount{
?public static int intWords = 0;
?public static int intLines = 0;
?public static int intChars = 0;
?public static void wc(InputStreamReader isr) throws IOException{
??int c = 0;
??boolean lastWhite = true;
??String whiteSpace = "\t\n\r";
??while((c=isr.read())!=-1){
???//Count characters.
???intChars++;
???//Count lines.
???if(c=='\n'){
????intLines++;
???}
???//Count words by detecting the start of a word
???int intIndex = whiteSpace.indexOf(c);
???if(intIndex == -1){
????if(lastWhite == true){
?????++intWords;
????}
????lastWhite = false;
???}else{
????lastWhite = true;
???}
??}
??if(intChars !=0){
???++intLines;
??}
?}
?public static void main(String[] args)
?{
??FileReader fr ;
??try{
???if(args.length ==0){
????//We're working with stdin
????wc(new InputStreamReader(System.in));
???}else{
????//We're working with a list of files.
????for(int i=0;i<args.length;i++){
?????fr = new FileReader(args[i]);
?????wc(fr);
????}
???}
??}catch(IOException e){
???return;
??}
??System.out.println(intLines + " " + intWords + " " + intChars);
?}
}
