Examples of java.util.Random

java.util.Random
An instance of this class is used to generate a stream of pseudorandom numbers. The class uses a 48-bit seed, which is modified using a linear congruential formula. (See Donald Knuth, The Art of Computer Programming, Volume 3, Section 3.2.1.)
If two instances of {@code Random} are created with the sameseed, and the same sequence of method calls is made for each, they will generate and return identical sequences of numbers. In order to guarantee this property, particular algorithms are specified for the class {@code Random}. Java implementations must use all the algorithms shown here for the class {@code Random}, for the sake of absolute portability of Java code. However, subclasses of class {@code Random}are permitted to use other algorithms, so long as they adhere to the general contracts for all the methods.
The algorithms implemented by class {@code Random} use a{@code protected} utility method that on each invocation can supplyup to 32 pseudorandomly generated bits.
Many applications will find the method {@link Math#random} simpler to use. @author Frank Yellin @version 1.47, 02/07/06 @since 1.0

        Connection conn;
        conn = getConnection("lob");
        Statement stat = conn.createStatement();
        stat.execute("create table test(id int primary key, data blob)");
        PreparedStatement prep;
        Random random = new Random();
        byte[] buff = new byte[500000];
        for (int i = 0; i < 10; i++) {
            prep = conn.prepareStatement("insert into test values(?, ?)");
            prep.setInt(1, i);
            random.setSeed(i);
            random.nextBytes(buff);
            prep.setBinaryStream(2, new ByteArrayInputStream(buff), -1);
            prep.execute();
        }
        if (upgraded) {
            if (config.memory) {
                stat.execute("update information_schema.lob_map set pos=null");
            } else {
                stat.execute("alter table information_schema.lob_map drop column pos");
                conn.close();
                conn = getConnection("lob");
            }
        }
        prep = conn.prepareStatement("select * from test where id = ?");
        for (int i = 0; i < 1; i++) {
            random.setSeed(i);
            random.nextBytes(buff);
            for (int j = 0; j < buff.length; j += 10000) {
                prep.setInt(1, i);
                ResultSet rs = prep.executeQuery();
                rs.next();
                InputStream in = rs.getBinaryStream(2);

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    private void testLobTransactions(int spaceLen) throws SQLException {
        deleteDb("lob");
        Connection conn = reconnect(null);
        conn.createStatement().execute("CREATE TABLE TEST(ID IDENTITY, DATA CLOB, DATA2 VARCHAR)");
        conn.setAutoCommit(false);
        Random random = new Random(0);
        int rows = 0;
        Savepoint sp = null;
        int len = getSize(100, 400);
        for (int i = 0; i < len; i++) {
            switch (random.nextInt(10)) {
            case 0:
                trace("insert");
                conn.createStatement().execute(
                        "INSERT INTO TEST(DATA, DATA2) VALUES('" + i + "' || SPACE(" + spaceLen + "), '" + i + "')");
                rows++;
                break;
            case 1:
                if (rows > 0) {
                    trace("delete");
                    conn.createStatement().execute("DELETE FROM TEST WHERE ID=" + random.nextInt(rows));
                }
                break;
            case 2:
                if (rows > 0) {
                    trace("update");
                    conn.createStatement().execute(
                            "UPDATE TEST SET DATA='x' || DATA, DATA2='x' || DATA2 WHERE ID=" + random.nextInt(rows));
                }
                break;
            case 3:
                if (rows > 0) {
                    trace("commit");

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    private static Reader getRandomReader(int len, int seed) {
        return new CharArrayReader(getRandomChars(len, seed));
    }


    private static char[] getRandomChars(int len, int seed) {
        Random random = new Random(seed);
        char[] buff = new char[len];
        for (int i = 0; i < len; i++) {
            char ch;
            do {
                ch = (char) random.nextInt(Character.MAX_VALUE);
                // UTF8: String.getBytes("UTF-8") only returns 1 byte for
                // 0xd800-0xdfff
            } while (ch >= 0xd800 && ch <= 0xdfff);
            buff[i] = ch;
        }

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        }
        return buff;
    }


    private static InputStream getRandomStream(int len, int seed) {
        Random random = new Random(seed);
        byte[] buff = new byte[len];
        random.nextBytes(buff);
        return new ByteArrayInputStream(buff);
    }

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            stat.execute("CREATE TABLE TEST(ID IDENTITY, NAME VARCHAR)");
            stat.execute("CREATE TABLE TEST2(ID IDENTITY, NAME VARCHAR)");
            stat.execute("CREATE TABLE TEST_META(ID INT)");
            PreparedStatement prep = conn.prepareStatement("INSERT INTO TEST(NAME) VALUES(?)");
            PreparedStatement prep2 = conn.prepareStatement("INSERT INTO TEST2(NAME) VALUES(?)");
            Random r = new Random(0);
//            Runnable stopper = new Runnable() {
//                public void run() {
//                    try {
//                        Thread.sleep(500);
//                    } catch (InterruptedException e) {
//                    }
//                    System.out.println("#Halt...");
//                    Runtime.getRuntime().halt(0);
//                }
//            };
//            new Thread(stopper).start();
            for (int i = 0; i < 2000; i++) {
                if (i == 100) {
                    System.out.println("#Running...");
                }
                if (r.nextInt(100) < 10) {
                    conn.createStatement().execute("ALTER TABLE TEST_META ALTER COLUMN ID INT DEFAULT 10");
                }
                if (r.nextBoolean()) {
                    if (r.nextBoolean()) {
                        prep.setString(1, new String(new char[r.nextInt(30) * 10]));
                        prep.execute();
                    } else {
                        prep2.setString(1, new String(new char[r.nextInt(30) * 10]));
                        prep2.execute();
                    }
                } else {
                    if (r.nextBoolean()) {
                        conn.createStatement().execute("UPDATE TEST SET NAME = NULL");
                    } else {
                        conn.createStatement().execute("UPDATE TEST2 SET NAME = NULL");
                    }
                }

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        Statement stat = conn.createStatement();
        int tableCount = getSize(2, 5);
        for (int i = 0; i < tableCount; i++) {
            stat.execute("create table t" + i + "(data varchar)");
        }
        Random random = new Random(1);
        int len = getSize(50, 500);
        for (int i = 0; i < len; i++) {
            String table = "t" + random.nextInt(tableCount);
            String sql;
            if (random.nextBoolean()) {
                sql = "insert into " + table + " values(space(100000))";
            } else {
                sql = "delete from " + table;
            }
            stat.execute(sql);

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        // Unicode problem:
        // The UCS code values 0xd800-0xdfff (UTF-16 surrogates)
        // as well as 0xfffe and 0xffff (UCS non-characters)
        // should not appear in conforming UTF-8 streams.
        // (String.getBytes("UTF-8") only returns 1 byte for 0xd800-0xdfff)
        Random random = new Random();
        random.setSeed(1);
        for (int i = 0; i < len; i++) {
            char c;
            do {
                c = (char) random.nextInt();
            } while (c >= 0xd800 && c <= 0xdfff);
            buff[i] = c;
        }
        String big = new String(buff);
        prep.setInt(1, 1);

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                "-cp", getClassPath(),
                getClass().getName(), "-url", url, "-user", user,
                "-password", password };
        deleteDb("killRestartMulti");
        int len = getSize(3, 10);
        Random random = new Random();
        for (int i = 0; i < len; i++) {
            Process p = Runtime.getRuntime().exec(procDef);
            InputStream in = p.getInputStream();
            OutputCatcher catcher = new OutputCatcher(in);
            catcher.start();
            while (true) {
                String s = catcher.readLine(5 * 60 * 1000);
                // System.out.println("> " + s);
                if (s == null) {
                    fail("No reply from process");
                } else if (!s.startsWith("#")) {
                    // System.out.println(s);
                    fail("Expected: #..., got: " + s);
                } else if (s.startsWith("#Running")) {
                    int sleep = 10 + random.nextInt(100);
                    Thread.sleep(sleep);
                    printTime("killing: " + i);
                    p.destroy();
                    p.waitFor();
                    break;

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            }
        }
        System.out.println("#Started; driver: " + driver + " url: " + url + " user: " + user + " password: " + password);
        try {
            System.out.println("#Starting...");
            Random random = new Random();
            boolean wasRunning = false;
            for (int i = 0; i < 3000; i++) {
                if (i > 1000 && connections.size() > 1 && tables.size() > 1) {
                    System.out.println("#Running connections: " + connections.size() + " tables: " + tables.size());
                    wasRunning = true;
                }
                if (connections.size() < 1) {
                    openConnection();
                }
                if (tables.size() < 1) {
                    createTable(random);
                }
                int p = random.nextInt(100);
                if ((p -= 2) <= 0) {
                    // 2%: open new connection
                    if (connections.size() < 5) {
                        openConnection();
                    }
                } else if ((p -= 1) <= 0) {
                    // 1%: close connection
                    if (connections.size() > 1) {
                        Connection conn = connections.remove(random.nextInt(connections.size()));
                        if (random.nextBoolean()) {
                            conn.close();
                        }
                    }
                } else if ((p -= 10) <= 0) {
                    // 10% create table
                    createTable(random);
                } else if ((p -= 20) <= 0) {
                    // 20% large insert, delete, or update
                    if (tables.size() > 0) {
                        Connection conn = connections.get(random.nextInt(connections.size()));
                        Statement stat = conn.createStatement();
                        String table = tables.get(random.nextInt(tables.size()));
                        if (random.nextBoolean()) {
                            // 10% insert
                            stat.execute("INSERT INTO " + table + "(NAME) SELECT 'Hello ' || X FROM SYSTEM_RANGE(0, 20)");
                        } else if (random.nextBoolean()) {
                            // 5% update
                            stat.execute("UPDATE " + table + " SET NAME='Hallo Welt'");
                        } else {
                            // 5% delete
                            stat.execute("DELETE FROM " + table);
                        }
                    }
                } else if ((p -= 5) < 0) {
                    // 5% truncate or drop table
                    if (tables.size() > 0) {
                        Connection conn = connections.get(random.nextInt(connections.size()));
                        Statement stat = conn.createStatement();
                        String table = tables.get(random.nextInt(tables.size()));
                        if (random.nextBoolean()) {
                            stat.execute("TRUNCATE TABLE " + table);
                        } else {
                            stat.execute("DROP TABLE " + table);
                            System.out.println("#Info table dropped: " + table);
                            tables.remove(table);
                        }
                    }
                } else if ((p -= 30) <= 0) {
                    // 30% insert
                    if (tables.size() > 0) {
                        Connection conn = connections.get(random.nextInt(connections.size()));
                        Statement stat = conn.createStatement();
                        String table = tables.get(random.nextInt(tables.size()));
                        stat.execute("INSERT INTO " + table + "(NAME) VALUES('Hello World')");
                    }
                } else {
                    // 32% delete
                    if (tables.size() > 0) {
                        Connection conn = connections.get(random.nextInt(connections.size()));
                        Statement stat = conn.createStatement();
                        String table = tables.get(random.nextInt(tables.size()));
                        stat.execute("DELETE FROM " + table + " WHERE ID = SELECT MIN(ID) FROM " + table);
                    }
                }
            }
            System.out.println("#Fail: end " + wasRunning);

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                "select a from test1 where b =1 or b =2 and b not in(2))) or c <>a) " +
                "and c in(0, 10) and c in(10, 0, 0) order by 1, 2, 3");
        p.set(1);
        p.execute();


        Random seedGenerator = new Random();
        String[] columns = new String[] { "a", "b", "c" };
        String[] values = new String[] { null, "0", "0", "1", "2", "10", "a", "?" };
        String[] compares = new String[] { "in(", "not in(", "=", "=", ">",
                "<", ">=", "<=", "<>", "in(select", "not in(select" };
        int size = getSize(100, 1000);
        for (int i = 0; i < size; i++) {
            long seed = seedGenerator.nextLong();
            println("seed: " + seed);
            Random random = new Random(seed);
            ArrayList<String> params = New.arrayList();
            String condition = getRandomCondition(random, params, columns, compares, values);
            //   System.out.println(condition + " " + params);
            PreparedStatement prep0 = conn.prepareStatement(
                    "select * from test0 where " + condition
                    + " order by 1, 2, 3");
            PreparedStatement prep1 = conn.prepareStatement(
                    "select * from test1 where " + condition
                    + " order by 1, 2, 3");
            for (int j = 0; j < params.size(); j++) {
                prep0.setString(j + 1, params.get(j));
                prep1.setString(j + 1, params.get(j));
            }
            ResultSet rs0 = prep0.executeQuery();
            ResultSet rs1 = prep1.executeQuery();
            assertEquals("seed: " + seed + " " + condition, rs0, rs1);
            if (params.size() > 0) {
                for (int j = 0; j < params.size(); j++) {
                    String value = values[random.nextInt(values.length - 2)];
                    params.set(j, value);
                    prep0.setString(j + 1, value);
                    prep1.setString(j + 1, value);
                }
                assertEquals("seed: " + seed + " " + condition, rs0, rs1);

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