算术编码压缩算法上的错误

Question

我正在尝试实现算术编码，这是一种压缩算法。这是压缩代码。当我编译时

线程中的异常"主" 在arithmetic.arithmeticcompress.main（arithmeticcompress.java:35）

它给了我这个错误。

来源

package arithmetic;
import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;

public class ArithmeticCompress {
public static void main(String[] args) throws IOException {

    File inputFile  = new File("D:\5.txt");
    File outputFile = new File("D:\new1.txt");
    // Read input file once to compute symbol frequencies
    //Line no 35
    FrequencyTable freqs = getFrequencies(inputFile);
    freqs.increment(256);  // EOF symbol gets a frequency of 1
    // Read input file again, compress with arithmetic coding, and write output file
    try (InputStream in = new BufferedInputStream(new FileInputStream(inputFile))) {
        try (BitOutputStream out = new BitOutputStream(new BufferedOutputStream(new FileOutputStream(outputFile)))) {
            writeFrequencies(out, freqs);
            compress(freqs, in, out);
        }
    }
}

// Returns a frequency table based on the bytes in the given file.
// Also contains an extra entry for symbol 256, whose frequency is set to 0.
private static FrequencyTable getFrequencies(File file) throws IOException {
    FrequencyTable freqs = new SimpleFrequencyTable(new int[257]);
    try (InputStream input = new BufferedInputStream(new FileInputStream(file))) {
        while (true) {
            int b = input.read();
            if (b == -1)
                break;
            freqs.increment(b);
        }
    }
    return freqs;
}

// To allow unit testing, this method is package-private instead of private.
static void writeFrequencies(BitOutputStream out, FrequencyTable freqs) throws IOException {
    for (int i = 0; i < 256; i++)
        writeInt(out, 32, freqs.get(i));
}

// To allow unit testing, this method is package-private instead of private.
static void compress(FrequencyTable freqs, InputStream in, BitOutputStream out) throws IOException {
    ArithmeticEncoder enc = new ArithmeticEncoder(out);
    while (true) {
        int symbol = in.read();
        if (symbol == -1)
            break;
        enc.write(freqs, symbol);
    }
    enc.write(freqs, 256);  // EOF
    enc.finish();  // Flush remaining code bits
}

// Writes an unsigned integer of the given bit width to the given stream.
private static void writeInt(BitOutputStream out, int numBits, int value) throws IOException {
    if (numBits < 0 || numBits > 32)
        throw new IllegalArgumentException();
    for (int i = numBits - 1; i >= 0; i--)
        out.write((value >>> i) & 1);  
}

}

Answer 1

好吧，这有点奇怪，因为这种源代码甚至不应该编译（因此不应该有任何Runtime Exception）：因为您的代码是参考类频率图，但该类不是在您的代码中定义，甚至没有导入？没有把握。但是通常，这将导致汇编错误，并且您应该无法运行此类代码 - 在这里，我想您正在使用某些IDE（例如Netbeans，也许是Eclipse），即使它不使用，也可以运行代码t编译 ->但在拉车期间会失败。

我建议在IDE中完全重建（清洁和编译）您的项目以显示您在代码中可能遇到的错误...