Java 中的无限循环

Question

因此，我尝试查看输入，并计算符合特定条件的单词（或者更确切地说，排除我不想计算的单词）。错误出现在以下代码中：

    BufferedReader br;
    BufferedWriter bw;
    String line;
    int identifiers = 0;
    boolean count = false;

    try
    {
        br = new BufferedReader(new FileReader("A1.input"));
        line = br.readLine();

        while(line != null)
        {
            StringTokenizer t = new StringTokenizer(line);
            String word;
            System.out.println(t.countTokens()); //for testing, keeps printing 6
            for(int c = 0; c < t.countTokens(); c++)
            {

                word = t.nextToken();
                count = true;
                if(Character.isDigit(word.charAt(0))) //if word begins with a number
                {
                    count = false; //do not count it
                } 
                if(count == true)
                {
                    for(String s : keywords)
                    {
                        if(s.equals(word)) //if the selected word is a keyword
                        {
                           count = false; //do not count it
                        }
                    }
                }

                System.out.println(word); //testing purposes

            }
            word = t.nextToken();
        }

这是输入文件：

INT f2(INT x, INT y ) 
  BEGIN 
  z := x*x - y*y;
RETURN z; 
 END 
 INT MAIN f1() 
 BEGIN
INT x;
READ(x, "A41.input");
INT y;
READ(y, "A42.input");
INT z;
z := f2(x,y) + f2(y,x);
WRITE (z, "A4.output"); 
END

正如上面代码中的注释所述，第一个 println 语句重复打印 6 （向我表明 while 循环无限重复）。第二个“测试目的”println 语句连续重复打印INT f2(INT x)。

Answer 1

看起来您从未真正阅读过文件的下一行。将此位：更改

try
{
    br = new BufferedReader(new FileReader("A1.input"));
    line = br.readLine();

    while(line != null)
    {

为：

try
{
    br = new BufferedReader(new FileReader("A1.input"));

    while((line = br.readLine()) != null)
    {

Answer 2

您使用 while() 仅评估当前行；因此，它永远不会null。将其更改为 if()。