import java.io.File; 
import java.io.FileWriter; 
import java.io.IOException; 
import java.io.PrintWriter; 
import java.util.ArrayList; 
import java.util.List; 

/** 
 * Test writing to disk by multiple threads all contending over the synchronized lock ... 
 */ 
public class TestSynchLockContention_J7 { 
public static void main(String[] args) throws IOException, InterruptedException { 

try ( ContendedResource resource = new ContendedResource("outfile.txt") ) { 
int contenderCount = Integer.parseInt(args[0]); 
int usageCount = Integer.parseInt(args[1]); 
int linesPerUse = Integer.parseInt(args[2]); 

List<Contender> contenders = new ArrayList<>(contenderCount); 
long start = System.currentTimeMillis(); 
for (int i = 0; i < contenderCount; i++) { 
Contender worker = new Contender(resource, linesPerUse, usageCount); 
contenders.add(worker); 
worker.start(); 
} 
for (Contender contender : contenders) { 
contender.join(); 
} 
long end = System.currentTimeMillis(); 
System.out.println("" + contenders.size() + " threads wrote total of " + resource.getBytecount() + " bytes in " + (end - start) + "ms."); 
} 
} 

private static class ContendedResource implements AutoCloseable { 
private long bytecount = 0; 
private PrintWriter out; 
public ContendedResource(String filename) throws IOException { 
File outfile = new File("outfile.txt"); 
out = new PrintWriter(new FileWriter(outfile)); 
} 
public synchronized long useResource(long lineslong) { 
for ( int i=0; i<lineslong; i++ ) { 
out.print("This is a bit of text written to the file 123456.\n"); 
} 
bytecount += 50*lineslong; 
return lineslong; 
} 

public synchronized long getBytecount() { 
return bytecount; 
} 

@Override 
public synchronized void close() { 
out.close(); 
} 
} 

private static class Contender extends Thread { 
private final ContendedResource resource; 
private final int linesPerUse; 
private final int usageCount; 

private Contender(ContendedResource resource, int linesPerUse, int usageCount) { 
this.resource = resource; 
this.linesPerUse = linesPerUse; 
this.usageCount = usageCount; 
} 

@Override 
public void run() { 
for ( int i=0; i<usageCount; i++ ) { 
resource.useResource(linesPerUse); 
} 
} 
} 
}