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Java example source code file (CopyMethods.java)

This example Java source code file (CopyMethods.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

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Java - Java tags/keywords

arraylist, class, error, hashmap, illegalaccessexception, illegalargumentexception, integer, method, not, object, random, reflection, runtimeexception, should, string, util

The CopyMethods.java Java example source code

/*
 * Copyright (c) 2005, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

/*
 * @test
 * @bug     4655503
 * @summary Test for array cloning and slicing methods.
 * @author  John Rose
 */

import java.util.*;
import java.lang.reflect.*;

public class CopyMethods {
    static int muzzle;  // if !=0, suppresses ("muzzles") messages

    static int maxLen = 40;  // maximum length of test arrays
    static int shortStepsNear = 4;  // interesting span near critical values
    static int downShift = 3;

    static int testCasesRun = 0;
    static long consing = 0;

    // very simple tests, mainly to test the framework itself
    static void simpleTests() {
        int[] a = (int[]) makeArray(3, int.class);
        if (muzzle == 0)
            System.out.println("int[] a = "+Arrays.toString(a));
        check(a.length == 3);
        check(a[0] == testValues[0]);
        check(a[1] == testValues[1]);
        check(a[2] == testValues[2]);
        checkArray(a, int.class, 3, 0, 3);
        // negative test of testing framework:
        for (int bad = -2; bad < a.length; bad++) {
            try {
                int[] aa = a.clone();
                if (bad < 0)  aa = new int[4];
                else          aa[bad] = 0;
                ++muzzle;
                // the following check should fail!
                if (bad == -2)
                    checkArray(new String[3], int.class, 0, 0, a.length);
                else
                    checkArray(aa, int.class, 0, 0, a.length);
                throw new Error("Should Not Reach Here");
            } catch (RuntimeException ee) {
                --muzzle;
                if (muzzle == 0)
                    System.out.println("Expected: "+ee);
            }
        }
        checkArray(Arrays.copyOf(a, 0), int.class, 0, 0, 3);
        checkArray(Arrays.copyOf(a, 1), int.class, 1, 0, 3);
        checkArray(Arrays.copyOf(a, 2), int.class, 2, 0, 3);
        checkArray(Arrays.copyOf(a, 3), int.class, 3, 0, 3);
        checkArray(Arrays.copyOf(a, 4), int.class, 4, 0, 3);

        // quick test of copyOfRange
        int[] ar = Arrays.copyOfRange(a, 1, 3);
        check(ar.length == 2);
        check(ar[0] == a[1]);
        check(ar[1] == a[2]);
        checkArray(ar, int.class, 2, 1, 2);
        ar = Arrays.copyOfRange(a, 2, 4);
        check(ar.length == 2);
        check(ar[0] == a[2]);
        check(ar[1] == 0);
        checkArray(ar, int.class, 2, 2, 1);
        ar = Arrays.copyOfRange(a, 3, 5);
        check(ar.length == 2);
        check(ar[0] == 0);
        check(ar[1] == 0);
        checkArray(ar, int.class, 2, 3, 0);
        byte[] ba = (byte[]) makeArray(3, byte.class);
        if (muzzle == 0)
            System.out.println("byte[] ba = "+Arrays.toString(ba));
        for (int j = 0; j <= ba.length+2; j++) {
            byte[] bb = Arrays.copyOf(ba, j);
            if (muzzle == 0)
                System.out.println("copyOf(ba,"+j+") = "+
                                   Arrays.toString(bb));
            checkArray(bb, byte.class, j, 0, ba.length);
            byte[] bbr = Arrays.copyOfRange(ba, 0, j);
            check(Arrays.equals(bb, bbr));
        }
        for (int i = 0; i <= a.length; i++) {
            for (int j = i; j <= a.length+2; j++) {
                byte[] br = Arrays.copyOfRange(ba, i, j);
                if (muzzle == 0)
                    System.out.println("copyOfRange(ba,"+i+","+j+") = "+
                                       Arrays.toString(br));
                checkArray(br, byte.class, j-i, i, ba.length-i);
            }
        }
        String[] sa = (String[]) makeArray(3, String.class);
        if (muzzle == 0)
            System.out.println("String[] sa = "+Arrays.toString(sa));
        check(sa[0].equals(Integer.toHexString(testValues[0])));
        check(sa[1].equals(Integer.toHexString(testValues[1])));
        check(sa[2].equals(Integer.toHexString(testValues[2])));
        checkArray(sa, String.class, sa.length, 0, sa.length);
        String[] sa4 = Arrays.copyOf(sa, sa.length+1);
        check(sa4[0] == sa[0]);
        check(sa4[1] == sa[1]);
        check(sa4[2] == sa[2]);
        check(sa4[sa.length] == null);
        checkArray(sa4, String.class, sa4.length, 0, sa.length);
        String[] sr4 = Arrays.copyOfRange(sa, 1, 5);
        check(sr4[0] == sa[1]);
        check(sr4[1] == sa[2]);
        check(sr4[2] == null);
        check(sr4[3] == null);
        checkArray(sr4, String.class, 4, 1, sa.length-1);
        if (muzzle == 0)
            System.out.println("simpleTests done");
    }

    // the framework:  a fixed series of test values
    static final int[] testValues;
    static {
        testValues = new int[1000];
        Random r = new Random();
        for (int i = 0; i < testValues.length; i++) {
            testValues[i] = r.nextInt();
        }
    }
    /** Return a canonical test value of a desired index and type.
     *  The original test values are random ints.  Derive other test
     *  values as follows:
     *  <pre>
     *  int tv = testValues[i]
     *  (C)tv                    C is byte, short, char, long, float, double
     *  (tv&1)!=0                C is boolean
     *  (Integer)tv              C is Object and tv%16 != 0
     *  null                     C is Object and tv%16 == 0
     *  Integer.toHexString(tv)  C is String and tv != 0
     *  null                     C is String and tv == 0
     *  </pre>
     *  are derived by ordinary Java coercions, except that boolean
     *  samples the LSB of the int value, and String is the hex numeral.
     *
     *  (Also, the 0th String is null, and the 0th Object mod 16 is null,
     *  regardless of the original int test value.)
     */
    static Object testValue(int i, Class<?> c) {
        int tv = testValues[i % testValues.length];
        if (i >= testValues.length)  tv ^= i;
        // Turn the canonical int to a float, boolean, String, whatever:
        return invoke(coercers.get(c), tv);
    }
    /** Build a test array of the given length,
     *  packed with a subsequence of the test values.
     *  The first element of the array is always testValue(0).
     */
    static Object makeArray(int len, Class<?> c) {
        Object a = Array.newInstance(c, len);
        for (int i = 0; i < len; i++) {
            Array.set(a, i, testValue(i, c));
        }
        return a;
    }
    /** Check that the given array has the required length.
     *  Check also that it is packed, up to firstNull, with
     *  a particular subsequence of the canonical test values.
     *  The subsequence must begin with a[0] == testValue(offset).
     *  At a[firstNull] and beyond, the array must contain null values.
     */
    static void checkArray(Object a, Class<?> c, int requiredLen, int offset, int firstNull) {
        check(c == a.getClass().getComponentType());
        Object nullValue = nullValues.get(c);
        // Note:  asserts in here are not part of the test program.
        // They verify the integrity of the test method itself.
        assert(nullValues.containsKey(c));

        int misses = 0;
        int firstMiss = -1;
        // Check required length first.
        int length = Array.getLength(a);
        if (length != requiredLen && requiredLen != -1) {
            if (muzzle == 0)
                System.out.println("*** a.length = "+length+" != "+requiredLen);
            ++misses;
        }

        for (int i = 0; i < length; i++) {
            Object tv = (i >= firstNull) ? nullValue : testValue(i+offset, c);
            Object ai = Array.get(a, i);
            if (!eq(ai, tv)) {
                if (muzzle == 0)
                    System.out.println("*** a["+i+"] = "+ai+" != "+tv);
                if (misses == 0)  firstMiss = i;
                if (++misses > 10)  break;
            }
        }
        if (misses != 0) {
            Method toString = toStrings.get(c);
            if (toString == null)  toString = toStrings.get(Object.class);
            throw new RuntimeException("checkArray failed at "+firstMiss
                                       +" "+c+"[]"
                                       +" : "+invoke(toString, a));
        }
    }
    // Typical comparison helper.  Why isn't this a method somewhere.
    static boolean eq(Object x, Object y) {
        return x == null? y == null: x.equals(y);
    }
    // Exception-ignoring invoke function.
    static Object invoke(Method m, Object... args) {
        Exception ex;
        try {
            return m.invoke(null, args);
        } catch (InvocationTargetException ee) {
            ex = ee;
        } catch (IllegalAccessException ee) {
            ex = ee;
        } catch (IllegalArgumentException ee) {
            ex = ee;
        }
        ArrayList<Object> call = new ArrayList();
        call.add(m); Collections.addAll(call, args);
        throw new RuntimeException(call+" : "+ex);
    }
    // version of assert() that runs unconditionally
    static void check(boolean z) {
        if (!z)  throw new RuntimeException("check failed");
    }


    /** Run about 10**5 distinct parameter combinations
     *  on copyOf and copyOfRange.  Use all primitive types,
     *  and String and Object.
     *  Try to all critical values, looking for fencepost errors.
     */
    static void fullTests(int maxLen, Class<?> c) {
        Method cloner      = cloners.get(c);
        assert(cloner != null) : c;
        Method cloneRanger = cloneRangers.get(c);
        // Note:  asserts in here are not part of the test program.
        // They verify the integrity of the test method itself.
        assert(cloneRanger != null) : c;
        for (int src = 0; src <= maxLen; src = inc(src, 0, maxLen)) {
            Object a = makeArray(src, c);
            for (int x : new ArrayList<Integer>()) {}
            for (int j = 0; j <= maxLen; j = inc(j, src, maxLen)) {
                // b = Arrays.copyOf(a, j);
                Object b = invoke(cloner, a, j);
                checkArray(b, c, j, 0, src);
                testCasesRun++;
                consing += j;

                int maxI = Math.min(src, j);
                for (int i = 0; i <= maxI; i = inc(i, src, maxI)) {
                    // r = Arrays.copyOfRange(a, i, j);
                    Object r = invoke(cloneRanger, a, i, j);
                    checkArray(r, c, j-i, i, src-i);
                    //System.out.println("case c="+c+" src="+src+" i="+i+" j="+j);
                    testCasesRun++;
                    consing += j-i;
                }
            }
        }
    }
    // Increment x by at least one.  Increment by a little more unless
    // it is near a critical value, either zero, crit1, or crit2.
    static int inc(int x, int crit1, int crit2) {
        int D = shortStepsNear;
        if (crit1 > crit2) { int t = crit1; crit1 = crit2; crit2 = t; }
        assert(crit1 <= crit2);
        assert(x <= crit2);  // next1 or next2 must be the limit value
        x += 1;
        if (x > D) {
            if (x < crit1-D) {
                x += (x << 1) >> downShift;  // giant step toward crit1-D
                if (x > crit1-D)  x = crit1-D;
            } else if (x >= crit1+D && x < crit2-D) {
                x += (x << 1) >> downShift;  // giant step toward crit2-D
                if (x > crit2-D)  x = crit2-D;
            }
        }
        return x;
    }

    public static void main(String[] av) {
        boolean verbose = (av.length != 0);
        muzzle = (verbose? 0: 1);
        if (muzzle == 0)
            System.out.println("test values: "+Arrays.toString(Arrays.copyOf(testValues, 5))+"...");

        simpleTests();

        muzzle = 0;  // turn on print statements (affects failures only)

        fullTests();
        if (verbose)
            System.out.println("ran "+testCasesRun+" tests, avg len="
                               +(float)consing/testCasesRun);

        // test much larger arrays, more sparsely
        maxLen = 500;
        shortStepsNear = 2;
        downShift = 0;
        testCasesRun = 0;
        consing = 0;
        fullTests();
        if (verbose)
            System.out.println("ran "+testCasesRun+" tests, avg len="
                               +(float)consing/testCasesRun);
    }

    static void fullTests() {
        for (Class<?> c : allTypes) {
            fullTests(maxLen, c);
        }
    }

    // We must run all the our tests on each of 8 distinct primitive types,
    // and two reference types (Object, String) for good measure.
    // This would be a pain to write out by hand, statically typed.
    // So, use reflection.  Following are the tables of methods we use.
    // (The initial simple tests exercise enough of the static typing
    // features of the API to ensure that they compile as advertised.)

    static Object  coerceToObject(int x) { return (x & 0xF) == 0? null: new Integer(x); }
    static String  coerceToString(int x) { return (x == 0)? null: Integer.toHexString(x); }
    static Integer coerceToInteger(int x) { return (x == 0)? null: x; }
    static byte    coerceToByte(int x) { return (byte)x; }
    static short   coerceToShort(int x) { return (short)x; }
    static int     coerceToInt(int x) { return x; }
    static long    coerceToLong(int x) { return x; }
    static char    coerceToChar(int x) { return (char)x; }
    static float   coerceToFloat(int x) { return x; }
    static double  coerceToDouble(int x) { return x; }
    static boolean coerceToBoolean(int x) { return (x&1) != 0; }

    static Integer[] copyOfIntegerArray(Object[] a, int len) {
        // This guy exercises the API based on a type-token.
        // Note the static typing.
        return Arrays.copyOf(a, len, Integer[].class);
    }
    static Integer[] copyOfIntegerArrayRange(Object[] a, int m, int n) {
        // This guy exercises the API based on a type-token.
        // Note the static typing.
        return Arrays.copyOfRange(a, m, n, Integer[].class);
    }

    static final List<Class allTypes
        = Arrays.asList(new Class<?>[]
                        {   Object.class, String.class, Integer.class,
                            byte.class, short.class, int.class, long.class,
                            char.class, float.class, double.class,
                            boolean.class
                        });
    static final HashMap<Class coercers;
    static final HashMap<Class cloners;
    static final HashMap<Class cloneRangers;
    static final HashMap<Class toStrings;
    static final HashMap<Class nullValues;
    static {
        coercers = new HashMap<Class();
        Method[] testMethods = CopyMethods.class.getDeclaredMethods();
        Method cia = null, ciar = null;
        for (int i = 0; i < testMethods.length; i++) {
            Method m = testMethods[i];
            if (!Modifier.isStatic(m.getModifiers()))  continue;
            Class<?> rt = m.getReturnType();
            if (m.getName().startsWith("coerceTo") && allTypes.contains(rt))
                coercers.put(m.getReturnType(), m);
            if (m.getName().equals("copyOfIntegerArray"))
                cia = m;
            if (m.getName().equals("copyOfIntegerArrayRange"))
                ciar = m;
        }
        Method[] arrayMethods = Arrays.class.getDeclaredMethods();
        cloners      = new HashMap<Class();
        cloneRangers = new HashMap<Class();
        toStrings    = new HashMap<Class();
        for (int i = 0; i < arrayMethods.length; i++) {
            Method m = arrayMethods[i];
            if (!Modifier.isStatic(m.getModifiers()))  continue;
            Class<?> rt = m.getReturnType();
            if (m.getName().equals("copyOf")
                && m.getParameterTypes().length == 2)
                cloners.put(rt.getComponentType(), m);
            if (m.getName().equals("copyOfRange")
                && m.getParameterTypes().length == 3)
                cloneRangers.put(rt.getComponentType(), m);
            if (m.getName().equals("toString")) {
                Class<?> pt = m.getParameterTypes()[0];
                toStrings.put(pt.getComponentType(), m);
            }
        }
        cloners.put(String.class, cloners.get(Object.class));
        cloneRangers.put(String.class, cloneRangers.get(Object.class));
        assert(cia != null);
        cloners.put(Integer.class, cia);
        assert(ciar != null);
        cloneRangers.put(Integer.class, ciar);
        nullValues = new HashMap<Class();
        for (Class<?> c : allTypes) {
            nullValues.put(c, invoke(coercers.get(c), 0));
        }
    }
}




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