如何使用Java中的StringReader类读取字符串？

Question

I have to read a String char by char using the String Reader Class. I have written this code:

String string = "Hello, World!";
StringReader stringReader = new StringReader(string);

while(stringReader.ready())
{
   System.out.println(stringReader.read());
}

But the loop doesn't end with the end of the string, it is infinite! Why?

I tried also to do that:

while(stringReader.read()!=-1)
{
   System.out.println(stringReader.read());
}

The loop isn't infinite...but it jumps some chars...how can I read all the String?

Answer 1

Try this:

    String str = "Hello, World!";

    //Create StringReader instance
    StringReader reader = new StringReader(str);
    int c = reader.read();
    while (c != -1){
        //Converting to character
        System.out.print((char)c);
        c = reader.read();
    }
    //Closing the file io
    reader.close();

Answer 2

The ready method tells you whether the next call to read won't block.

Returns: True if the next read() is guaranteed not to block for input, false otherwise.

Once you get to the end of the string, it certainly won't block; you've reached the end of the string. With a String , the contents are already present; a StringReader should always return true for ready .

You are skipping characters when you call read twice per loop -- once in the while condition and once in the body. Assign it to a variable instead.

int c;
while((c = stringReader.read()) !=  -1)
{
    System.out.println((char) c);
}

You can also do what you'd normally do any other kind of Reader -- wrap it in a BufferedReader so you can call nextLine or wrap it in a Scanner .

BufferedReader bf = new BufferedReader(stringReader);

or

Scanner strScanner = new Scanner(stringReader);