Java by API/java.util.zip/Checksum

Checksum: getValue()

   <source lang="java">
      

import java.io.FileInputStream; import java.io.IOException; import java.io.InputStream; import java.util.zip.CRC32; import java.util.zip.Checksum; public class Main {

 public static void main(String[] args) throws IOException {
   FileInputStream fin = new FileInputStream(args[0]);
   System.out.println(args[0] + ":\t" + getCRC32(fin));
   fin.close();
 }
 public static long getCRC32(InputStream in) throws IOException {
   Checksum cs = new CRC32();
   for (int b = in.read(); b != -1; b = in.read()) {
     cs.update(b);
   }
   return cs.getValue();
 }

}

 </source>
   
  
 
  

Checksum: reset()

   <source lang="java">

import java.util.zip.CRC32; import java.util.zip.Checksum; public class Main {

 public static void main(String[] argv) throws Exception {
   byte[] bytes = "some data".getBytes();
   // Compute Adler-32 checksum
   Checksum checksumEngine = new CRC32();
   checksumEngine.update(bytes, 0, bytes.length);
   long checksum = checksumEngine.getValue();
   checksumEngine.reset();
 }

}

 </source>
   
  
 
  

Checksum: update(int b)

   <source lang="java">
      

import java.io.FileInputStream; import java.io.IOException; import java.io.InputStream; import java.util.zip.CRC32; import java.util.zip.Checksum; public class Main {

 public static void main(String[] args) throws IOException {
   FileInputStream fin = new FileInputStream(args[0]);
   System.out.println(args[0] + ":\t" + getCRC32(fin));
   fin.close();
 }
 public static long getCRC32(InputStream in) throws IOException {
   Checksum cs = new CRC32();
   for (int b = in.read(); b != -1; b = in.read()) {
     cs.update(b);
   }
   return cs.getValue();
 }

}

 </source>
   
  
 
  

implements Checksum

   <source lang="java">

import java.util.zip.Checksum; public class ParityChecksum implements Checksum {

 long checksum = 0;
 public void update(int b) {
   int numOneBits = 0;
   for (int i = 1; i < 256; i *= 2) {
     if ((b & i) != 0)
       numOneBits++;
   }
   checksum = (checksum + numOneBits) % 2;
 }
 public void update(byte data[], int offset, int length) {
   for (int i = offset; i < offset + length; i++) {
     this.update(data[i]);
   }
 }
 public long getValue() {
   return checksum;
 }
 public void reset() {
   checksum = 0;
 }

}

 </source>