hadoop源碼閱讀之代碼抽取

1

package com.m;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.lang.management.ManagementFactory;
import java.net.InetAddress;
import java.net.NetworkInterface;
import java.net.SocketException;
import java.util.Enumeration;
import java.util.Locale;
import java.util.TreeSet;

/**
 *     解析字符串中的參數, 並填充實際的內容(進程名、ip、進程號)<br>
 */
public class Test {
    public static void main(String[] args) {
        String fmt = "%{tname}/%{ip}";
        StringBuilder bld = new StringBuilder();
        StringBuilder varBld = null;
        boolean escaping = false;
        int varSeen = 0;
        int i = 0;

        for(int len = fmt.length(); i < len; ++i) {
            char c = fmt.charAt(i);
            if (c == '\\' && !escaping) {
                escaping = true;
            } else {
                switch(varSeen) {
                    case 0:
                        if (c == '%' && !escaping) {
                            varSeen = 1;
                            break;
                        }

                        escaping = false;
                        varSeen = 0;
                        bld.append(c);
                        break;
                    case 1:
                        if (c == '{' && !escaping) {
                            varSeen = 2;
                            varBld = new StringBuilder();
                            break;
                        }

                        escaping = false;
                        varSeen = 0;
                        bld.append("%").append(c);
                        break;
                    default:
                        if (c == '}' && !escaping) {
                            String var = varBld.toString();
                            bld.append(processShellVar(var));
                            varBld = null;
                            varSeen = 0;
                        } else {
                            escaping = false;
                            varBld.append(c);
                            ++varSeen;
                        }
                }
            }
        }

        if (varSeen > 0) {
            System.out.println("Unterminated process ID substitution variable at the end of format string " + fmt);
        }

        System.out.println(bld.toString());
    }

    private static String processShellVar(String var) {
        if (var.equals("tname")) {
            return "tname1";
        } else if (var.equals("pname")) {
            return getProcessName();
        } else if (var.equals("ip")) {
            return getBestIpString();
        } else if (var.equals("pid")) {
            return Long.valueOf(getOsPid()).toString();
        } else {
            System.out.println("unknown ProcessID variable " + var);
            return "";
        }
    }

    static String getProcessName() {
        String cmdLine = System.getProperty("sun.java.command");
        if (cmdLine != null && !cmdLine.isEmpty()) {
            String fullClassName = cmdLine.split("\\s+")[0];
            String[] classParts = fullClassName.split("\\.");
            cmdLine = classParts[classParts.length - 1];
        }

        return cmdLine != null && !cmdLine.isEmpty() ? cmdLine : "Unknown";
    }

    static String getBestIpString() {
        Enumeration ifaces;
        try {
            ifaces = NetworkInterface.getNetworkInterfaces();
        } catch (SocketException var6) {
            System.out.println("Error getting network interfaces:" + var6);
            return "127.0.0.1";
        }

        TreeSet<String> siteLocalCandidates = new TreeSet();
        TreeSet candidates = new TreeSet();

        while(ifaces.hasMoreElements()) {
            NetworkInterface iface = (NetworkInterface)ifaces.nextElement();
            Enumeration addrs = iface.getInetAddresses();

            while(addrs.hasMoreElements()) {
                InetAddress addr = (InetAddress)addrs.nextElement();
                if (!addr.isLoopbackAddress()) {
                    if (addr.isSiteLocalAddress()) {
                        siteLocalCandidates.add(addr.getHostAddress());
                    } else {
                        candidates.add(addr.getHostAddress());
                    }
                }
            }
        }

        if (!siteLocalCandidates.isEmpty()) {
            return (String)siteLocalCandidates.first();
        } else if (!candidates.isEmpty()) {
            return (String)candidates.first();
        } else {
            return "127.0.0.1";
        }
    }

    static long getOsPid() {
        return System.getProperty("os.name", "generic").toLowerCase(Locale.ENGLISH).contains("windows") ? getOsPidFromManagementFactory() : getOsPidFromShellPpid();
    }

    private static long getOsPidFromManagementFactory() {
        try {
            return Long.parseLong(ManagementFactory.getRuntimeMXBean().getName().split("@")[0]);
        } catch (NumberFormatException var1) {
            System.out.println("Failed to get the operating system process ID from the name of the managed bean for the JVM."  + var1);
            return 0L;
        }
    }


    private static long getOsPidFromShellPpid() {
        Process p = null;
        StringBuilder sb = new StringBuilder();

        label106: {
            long var5;
            try {
                p = (new ProcessBuilder(new String[]{"/usr/bin/env", "sh", "-c", "echo $PPID"})).redirectErrorStream(true).start();
                BufferedReader reader = new BufferedReader(new InputStreamReader(p.getInputStream()));
                String line = "";

                while((line = reader.readLine()) != null) {
                    sb.append(line.trim());
                }

                int exitVal = p.waitFor();
                if (exitVal != 0) {
                    throw new IOException("Process exited with error code " + Integer.valueOf(exitVal).toString());
                }
                break label106;
            } catch (InterruptedException var13) {
                System.out.println("Interrupted while getting operating system pid from the shell." +  var13);
                var5 = 0L;
                return var5;
            } catch (IOException var14) {
                System.out.println("Error getting operating system pid from the shell." + var14);
                var5 = 0L;
            } finally {
                if (p != null) {
                    p.destroy();
                }

            }

            return var5;
        }

        try {
            return Long.parseLong(sb.toString());
        } catch (NumberFormatException var12) {
            System.out.println("Error parsing operating system pid from the shell." +  var12);
            return 0L;
        }
    }
}

2

package com.m;

import org.apache.htrace.core.SpanId;

import java.util.concurrent.ThreadLocalRandom;

/**
 * 抽取自: htrace包中的sparnId類<br>
 */
public class Test {
    public static void main(String[] args) {
        new SpanId(SpanId.nonZeroRand64(), SpanId.nonZeroRand64());
    }

    /*
     * 根據程序上bai下文環境，Java關鍵字final有“這是無法du改變的”zhi或者“終態的”含義，它可以dao修飾非抽象類、非抽象類成員方法和變量。
     * final類不能被繼承，沒有子類，final類中的方法默認是final的。
     * final方法不能被子類的方法覆蓋，但可以被繼承。
     * final成員變量表示常量，只能被賦值一次，賦值後值不再改變。
     * final不能用於修飾構造方法。
     * 注意：父類的private成員方法是不能被子類方法覆蓋的，因此private類型的方法默認是final類型的。
     */
    public final static class SpanId implements Comparable<SpanId>{
        private static final int SPAN_ID_STRING_LENGTH = 32;
        private final long high; // final成員變量表示常量，只能被賦值一次，賦值後值不再改變。
        private final long low; // final成員變量表示常量，只能被賦值一次，賦值後值不再改變。

        public static org.apache.htrace.core.SpanId fromString(String str) {
            if (str.length() != SPAN_ID_STRING_LENGTH) {
                throw new RuntimeException("Invalid SpanID string: length was not " +
                        SPAN_ID_STRING_LENGTH);
            }
            long high =
                    ((Long.parseLong(str.substring(0, 8), 16)) << 32) |
                            (Long.parseLong(str.substring(8, 16), 16));
            long low =
                    ((Long.parseLong(str.substring(16, 24), 16)) << 32) |
                            (Long.parseLong(str.substring(24, 32), 16));
            return new org.apache.htrace.core.SpanId(high, low);
        }

        public SpanId(long high, long low) {
            this.high = high;
            this.low = low;
        }
        private static long nonZeroRand64() {
            while (true) {
                long r = ThreadLocalRandom.current().nextLong();
                if (r != 0) {
                    return r;
                }
            }
        }

        public static org.apache.htrace.core.SpanId fromRandom() {
            return new org.apache.htrace.core.SpanId(nonZeroRand64(), nonZeroRand64());
        }


        @Override
        public String toString() {
            return String.format("%08x%08x%08x%08x",
                    (0x00000000ffffffffL & (high >> 32)),
                    (0x00000000ffffffffL & high),
                    (0x00000000ffffffffL & (low >> 32)),
                    (0x00000000ffffffffL & low));
        }

        @Override
        public int hashCode() {
            return (int)((0xffffffff & (high >> 32))) ^
                    (int)((0xffffffff & (high >> 0))) ^
                    (int)((0xffffffff & (low >> 32))) ^
                    (int)((0xffffffff & (low >> 0)));
        }

        @Override
        public int compareTo(SpanId other) {
            int cmp = compareAsUnsigned(high, other.high);
            if (cmp != 0) {
                return cmp;
            }
            return compareAsUnsigned(low, other.low);
        }

        private static int compareAsUnsigned(long a, long b) {
            boolean aSign = a < 0;
            boolean bSign = b < 0;
            if (aSign != bSign) {
                if (aSign) {
                    return 1;
                } else {
                    return -1;
                }
            }
            if (aSign) {
                a = -a;
                b = -b;
            }
            if (a < b) {
                return -1;
            } else if (a > b) {
                return 1;
            } else {
                return 0;
            }
        }

        @Override
        public boolean equals(Object o) {
            if (!(o instanceof SpanId)) {
                return false;
            }
            SpanId other = (SpanId)o;
            return ((other.high == high) && (other.low == low));
        }

    }
}

3

package com.m;

import org.apache.htrace.core.SpanId;

import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.ThreadLocalRandom;

/**
 * 有趣的現象<br>
 */
public class Test {
    public static void main(String[] args) {
        final List<String> list = new ArrayList<>();
        list.add("1");
        list.add("2");
        // 有趣的現象:   抽象類中沒有任何成員變量, 但是new一個抽象類後，如果內部引用外部的final變量，就會相當於抽象類的實現類中存在了final類型的成員變量, 通過調試就可以看出來
        abstractTest abstractTest = new abstractTest() {
            @Override
            public void test() {
                for (String str : list) {
                    System.out.println(str);
                }
            }
        };
        System.out.println(abstractTest);
    }

    public abstract  static class abstractTest {
        public abstract void test();

        public void test1() {
            System.out.println("test1");
        }
    }
}