获取上G的文件行数的最快速的代码占用内存少
占用内存少，而且最快的获取海量文件的java代码原文：http://www.zuidaima.com/share/1550463225072640.htm
代码package com.zuidaima.test;
import java.io.BufferedInputStream;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.LineNumberReader;
import org.databene.contiperf.PerfTest;
import org.databene.contiperf.junit.ContiPerfRule;
import org.junit.Rule;
import org.junit.Test;
/**
*@author www.zuidaima.com
**/
public class HugeFileLineCounter {
public static final String hugeFilePath = "c:/test.log";
@Rule
public ContiPerfRule rule = new ContiPerfRule();
// samples: 20
// max: 1353
// average: 1308.55
// median: 1309
@Test
@PerfTest(invocations = 20, threads = 1)
public void count1() throws IOException {
LineNumberReader reader = new LineNumberReader(new FileReader(new File(
hugeFilePath)));
reader.skip(Long.MAX_VALUE);
reader.close();
System.out.println(reader.getLineNumber());
}
// most quickly sloution
// samples: 20
// max: 654
// average: 507.6
// median: 494
@Test
@PerfTest(invocations = 20, threads = 1)
public void count2() throws IOException {
InputStream is = new BufferedInputStream(new FileInputStream(
hugeFilePath));
int count = 0;
try {
byte[] c = new byte;
int readChars = 0;
while ((readChars = is.read(c)) != -1) {
for (int i = 0; i < readChars; ++i) {
if (c == '\n')
++count;
}
}
} finally {
is.close();
}
System.out.println(count);
}
// samples: 20
// max: 622
// average: 504.8
// median: 495
@Test
@PerfTest(invocations = 20, threads = 1)
public void count3() throws IOException {
InputStream is = new BufferedInputStream(new FileInputStream(
hugeFilePath));
int count = 0;
try {
byte[] c = new byte;
int readChars = 0;
while ((readChars = is.read(c)) != -1) {
for (int i = 0; i < readChars; ++i) {
if (c == '\n')
++count;
}
}
} finally {
is.close();
}
System.out.println(count);
}
// samples: 20
// max: 1138
// average: 1050.75
// median: 1047
@Test
@PerfTest(invocations = 20, threads = 1)
public void count4() throws IOException {
BufferedReader reader = new BufferedReader(new InputStreamReader(
new FileInputStream(hugeFilePath), "UTF8"));
int count = 0;
try {
char[] c = new char;
int readChars = 0;
while ((readChars = reader.read(c)) != -1) {
for (int i = 0; i < readChars; ++i) {
if (c == '\n')
++count;
}
}
} finally {
reader.close();
}
System.out.println(count);
}
}
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