Merge remote-tracking branch 'upstream/master'

2023-10-06 21:29:32 +02:00
parent 7e1d5991e6 77d51bcb95
commit a8290e27cd
65 changed files with 1040 additions and 104 deletions
@@ -1,3 +1,5 @@
 ## Relevant Articles
 - [Sequenced Collections in Java 21](https://www.baeldung.com/java-21-sequenced-collections)
 - [String Templates in Java 21](https://www.baeldung.com/java-21-string-templates)
+- [Unnamed Classes and Instance Main Methods in Java 21](https://www.baeldung.com/java-21-unnamed-class-instance-main)
+- [Unnamed Patterns and Variables in Java 21](https://www.baeldung.com/java-unnamed-patterns-variables)
@@ -5,3 +5,4 @@ This module contains articles about Java Character Class
 ### Relevant Articles: 
 - [Character#isAlphabetic vs. Character#isLetter](https://www.baeldung.com/java-character-isletter-isalphabetic)
 - [Difference Between Java’s “char” and “String”](https://www.baeldung.com/java-char-vs-string)
+- [Increment Character in Java](https://www.baeldung.com/java-char-sequence)
@@ -5,4 +5,6 @@
 ### Relevant Articles:
 - [Introduction to Roaring Bitmap](https://www.baeldung.com/java-roaring-bitmap-intro)
 - [Creating Custom Iterator in Java](https://www.baeldung.com/java-creating-custom-iterator)
+- [Difference Between Arrays.sort() and Collections.sort()](https://www.baeldung.com/java-arrays-collections-sort-methods)
+- [Skipping the First Iteration in Java](https://www.baeldung.com/java-skip-first-iteration)
 - More articles: [[<-- prev]](/core-java-modules/core-java-collections-4)
@@ -3,4 +3,4 @@
 This module contains articles about the Java ArrayList collection

 ### Relevant Articles:
- [Create an ArrayList with Multiple Object Types](https://www.baeldung.com/arraylist-with-multiple-object-types)
+- [Create an ArrayList with Multiple Object Types](https://www.baeldung.com/java-arraylist-multiple-object-types)
@@ -3,3 +3,4 @@
 This module contains articles about conversions among Collection types in Java.

 ### Relevant Articles:
+- [Converting HashMap Values to an ArrayList in Java](https://www.baeldung.com/java-hashmap-arraylist)
@@ -12,10 +12,10 @@ public class EpochTimeToLocalDateTimeConverterUnitTest {
    @Test
    public void testConvertEpochTimeToLocalDateTime() {
        long epochTimeMillis = 1624962431000L; // Example epoch time in milliseconds
-        LocalDateTime expectedDateTime = LocalDateTime.of(2021, 6, 29, 12, 13, 51);
+        LocalDateTime expectedDateTime = LocalDateTime.of(2021, 6, 29, 10, 27, 11);

        Instant instant = Instant.ofEpochMilli(epochTimeMillis);
-        ZoneId zoneId = ZoneId.systemDefault();
+        ZoneId zoneId = ZoneId.of("UTC");
        LocalDateTime actualDateTime = instant.atZone(zoneId).toLocalDateTime();

        assertEquals(expectedDateTime, actualDateTime);
@@ -3,6 +3,6 @@
 This module contains articles about core Java input and output (IO)

 ### Relevant Articles: 
-
+- [Get File Extension From MIME Type in Java](https://www.baeldung.com/java-mime-type-file-extension)
 - [[<-- Prev]](/core-java-modules/core-java-io-4)

@@ -25,8 +25,12 @@
            <version>${commons-codec}</version>
            <scope>test</scope>
        </dependency>
+        <dependency>
+            <groupId>com.google.guava</groupId>
+            <artifactId>guava</artifactId>
+            <version>${guava.version}</version>
+        </dependency>
    </dependencies>
-
    <build>
        <finalName>core-java-numbers-6</finalName>
        <resources>
@@ -39,5 +43,6 @@

    <properties>
        <commons-codec>1.15</commons-codec>
+        <guava.version>32.1.2-jre</guava.version>
    </properties>
 </project>
@@ -0,0 +1,8 @@
+package com.baeldung.bigintegerroot;
+
+public class BenchmarkRunner {
+    public static void main(String[] args) throws Exception {
+        org.openjdk.jmh.Main.main(args);
+    }
+}
+
@@ -0,0 +1,10 @@
+package com.baeldung.bigintegerroot;
+
+public class BigIntegerHolder {
+
+    private BigIntegerHolder() {
+    }
+    public static final String BIG_NUMBER = "179769313000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000";
+    public static final String VERY_BIG_NUMBER = "32473927492374927934284792374923749237498723048012834324739274923749279342847923749237492374987230480128343247392749237492793428479237492374923749872304801283432473927492374927934284792374923749237498723048012834324739274923749279342847923749237492374987230480128343247392749237492793428479237492374923749872304801283432473927492374927934284792374923749237498723048012834324739274923749279342847923749237492374987230480128343247392749237492793428479237492374923749872304801283432473927492374927934284792374923749237498723048012834324739274923749279342847923749237492374987230480128343247392749237492793428479237492374923749872304801283432473927492374927934284792374923749237498723048012834324739274923749279342847923749237492374987230480128343247392749237492793428479237492374923749872304801283432473927492374927934284792374923749237498723048012834324739274923749279342847923749237492374987230480128343247392749237492793428479237492374923749872304801283432473927492374927934284792374923749237498723048012834324739274923749279342847923749237492374987230480128343247392749237492793428479237492374923749872304801283432473927492374927934284792374923749237498723048012834324739274923749279342847923749237492374987230480128343247392749237492793428479237492374923749872304801283432473927492374927934284792374923749237498723048012834324739274923749279342847923749237492374987230480128343247392749237492793428479237492374923749872304801283432473927492374927934284792374923749237498723048012834324739274923749279342847923749237492374987230480128343247392749237492793428479237492374923749872304801283432473927492374927934284792374923749237498723048012834324739274923749279342847923749237492374987230480128343247392749237492793428479237492374923749872304801283432473927492374927934284792374923749237498723048012834";
+    public static final String INSANELY_BIG_NUMBER = "3247392749237492793428479237492374923749872304801283432473927492374927934284792374923749237498723048012834324739274923749279342847923749237492374987230480128343247392749237492793428479237492374923749872304801283432473927492374927934284792374923749237498723048012834324739274923749279342847923749237492374987230480128343247392749237492793428479237492374923749872304801283432473927492374927934284792374923749237498723048012834324739274923749279342847923749237492374987230480128343247392749237492793428479237492374923749872304801283432473927492374927934284792374923749237498723048012834324739274923749279342847923749237492374987230480128343247392749237492793428479237492374923749872304801283432473927492374927934284792374923749237498723048012834324739274923749279342847923749237492374987230480128343247392749237492793428479237492374923749872304801283432473927492374927934284792374923749237498723048012834324739274923749279342847923749237492374987230480128343247392749237492793428479237492374923749872304801283432473927492374927934284792374923749237498723048012834324739274923749279342847923749237492374987230480128343247392749237492793428479237492374923749872304801283432473927492374927934284792374923749237498723048012834324739274923749279342847923749237492374987230480128343247392749237492793428479237492374923749872304801283432473927492374927934284792374923749237498723048012834324739274923749279342847923749237492374987230480128343247392749237492793428479237492374923749872304801283432473927492374927934284792374923749237498723048012834324739274923749279342847923749237492374987230480128343247392749237492793428479237492374923749872304801283432473927492374927934284792374923749237498723048012834324739274923749279342847923749237492374987230480128343247392749237492793428479237492374923749872304801283432473927492374927934284792374923749237498723048012834324739274923749279342847923749237492374987230480128343247392749237492793428479237492374923749872304801283432473927492374927934284792374923749237498723048012834324739274923749279342847923749237492374987230480128343247392749237492793428479237492374923749872304801283432473927492374927934284792374923749237498723048012834324739274923749279342847923749237492374987230480128343247392749237492793428479237492374923749872304801283432473927492374927934284792374923749237498723048012834324739274923749279342847923749237492374987230480128343247392749237492793428479237492374923749872304801283432473927492374927934284792374923749237498723048012834324739274923749279342847923749237492374987230480128343247392749237492793428479237492374923749872304801283432473927492374927934284792374923749237498723048012834324739274923749279342847923749237492374987230480128343247392749237492793428479237492374923749872304801283432473927492374927934284792374923749237498723048012834324739274923749279342847923749237492374987230480128343247392749237492793428479237492374923749872304801283432473927492374927934284792374923749237498723048012834324739274923749279342847923749237492374987230480128343247392749237492793428479237492374923749872304801283432473927492374927934284792374923749237498723048012834324739274923749279342847923749237492374987230480128343247392749237492793428479237492374923749872304801283432473927492374927934284792374923749237498723048012834324739274923749279342847923749237492374987230480128343247392749237492793428479237492374923749872304801283432473927492374927934284792374923749237498723048012834324739274923749279342847923749237492374987230480128343247392749237492793428479237492374923749872304801283432473927492374927934284792374923749237498723048012834";
+}
@@ -0,0 +1,60 @@
+package com.baeldung.bigintegerroot;
+
+import static com.baeldung.bigintegerroot.BigIntegerHolder.*;
+
+import com.baeldung.bigintegerroot.algorithms.Newton;
+import com.baeldung.bigintegerroot.algorithms.NewtonPlus;
+import com.google.common.math.BigIntegerMath;
+import java.math.BigInteger;
+import java.math.RoundingMode;
+import java.util.concurrent.TimeUnit;
+import org.openjdk.jmh.annotations.Benchmark;
+import org.openjdk.jmh.annotations.BenchmarkMode;
+import org.openjdk.jmh.annotations.Fork;
+import org.openjdk.jmh.annotations.Measurement;
+import org.openjdk.jmh.annotations.Mode;
+import org.openjdk.jmh.annotations.Param;
+import org.openjdk.jmh.annotations.Scope;
+import org.openjdk.jmh.annotations.State;
+import org.openjdk.jmh.annotations.Warmup;
+import org.openjdk.jmh.infra.Blackhole;
+
+@Warmup(iterations = 1)
+@Measurement(iterations = 1, time = 1, timeUnit = TimeUnit.MINUTES)
+@Fork(1)
+@State(Scope.Benchmark)
+public class BigIntegerSquareRootBenchmark {
+
+    @Param({BIG_NUMBER, VERY_BIG_NUMBER, INSANELY_BIG_NUMBER})
+    public String number;
+    @Benchmark
+    @BenchmarkMode(Mode.Throughput)
+    public void calculateRootWithJava(Blackhole blackhole) {
+        final BigInteger integer = new BigInteger(number);
+        final BigInteger root = integer.sqrt();
+        blackhole.consume(root);
+    }
+
+    @Benchmark
+    @BenchmarkMode(Mode.Throughput)
+    public void calculateRootWithGuava(Blackhole blackhole) {
+        final BigInteger integer = new BigInteger(number);
+        final BigInteger root = BigIntegerMath.sqrt(integer, RoundingMode.DOWN);
+        blackhole.consume(root);
+    }
+
+    @Benchmark
+    @BenchmarkMode(Mode.Throughput)
+    public void calculateRootWithNewtonPlus(Blackhole blackhole) {
+        final BigInteger integer = new BigInteger(number);
+        final BigInteger root = NewtonPlus.sqrt(integer);
+        blackhole.consume(root);
+    }
+    @Benchmark
+    @BenchmarkMode(Mode.Throughput)
+    public void calculateRootWithNewton(Blackhole blackhole) {
+        final BigInteger integer = new BigInteger(number);
+        final BigInteger root = Newton.sqrt(integer);
+        blackhole.consume(root);
+    }
+}
@@ -0,0 +1,29 @@
+package com.baeldung.bigintegerroot.algorithms;
+
+import java.math.BigInteger;
+
+public class Newton {
+
+    private Newton() {
+    }
+
+    public static BigInteger sqrt(BigInteger n) {
+        // Initial approximation
+        BigInteger x = n.divide(BigInteger.TWO);
+
+        // Tolerance level (small positive integer)
+        BigInteger tolerance = BigInteger.ONE;
+
+        while (true) {
+            // x_new = 0.5 * (x + n / x)
+            BigInteger xNew = x.add(n.divide(x)).divide(BigInteger.TWO);
+
+            // Check for convergence within tolerance
+            if (x.subtract(xNew).abs().compareTo(tolerance) <= 0) {
+                return xNew;
+            }
+
+            x = xNew;
+        }
+    }
+}
@@ -0,0 +1,108 @@
+package com.baeldung.bigintegerroot.algorithms;
+
+import java.math.BigInteger;
+
+public class NewtonPlus {
+
+    private NewtonPlus() {
+    }
+
+    // A fast square root by Ryan Scott White.
+    public static BigInteger sqrt(BigInteger x) {
+        if (x.compareTo(BigInteger.valueOf(144838757784765629L)) < 0) {
+            long xAsLong = x.longValue();
+            long vInt = (long)Math.sqrt(xAsLong);
+            if (vInt * vInt > xAsLong)
+                vInt--;
+            return BigInteger.valueOf(vInt); }
+
+        double xAsDub = x.doubleValue();
+        BigInteger val;
+        if (xAsDub < 2.1267e37) // 2.12e37 largest here
+        // since sqrt(long.max*long.max) > long.max
+        {
+            long vInt = (long)Math.sqrt(xAsDub);
+            val = BigInteger.valueOf
+                ((vInt + x.divide(BigInteger.valueOf(vInt)).longValue()) >> 1);
+        }
+        else if (xAsDub < 4.3322e127) {
+            // Convert a double to a BigInteger
+            long bits = Double.doubleToLongBits(Math.sqrt(xAsDub));
+            int exp = ((int) (bits >> 52) & 0x7ff) - 1075;
+            val = BigInteger.valueOf((bits & ((1L << 52)) - 1) | (1L << 52)).shiftLeft(exp);
+
+            val = x.divide(val).add(val).shiftRight(1);
+            if (xAsDub > 2e63) {
+                val = x.divide(val).add(val).shiftRight(1); }
+        }
+        else // handle large numbers over 4.3322e127
+        {
+            int xLen = x.bitLength();
+            int wantedPrecision = ((xLen + 1) / 2);
+            int xLenMod = xLen + (xLen & 1) + 1;
+
+            //////// Do the first Sqrt on Hardware ////////
+            long tempX = x.shiftRight(xLenMod - 63).longValue();
+            double tempSqrt1 = Math.sqrt(tempX);
+            long valLong = Double.doubleToLongBits(tempSqrt1) & 0x1fffffffffffffL;
+
+            if (valLong == 0)
+                valLong = 1L << 53;
+
+            //////// Classic Newton Iterations ////////
+            val = BigInteger.valueOf(valLong).shiftLeft(53 - 1)
+                .add((x.shiftRight(xLenMod -
+                                   (3 * 53))).divide(BigInteger.valueOf(valLong)));
+
+            int size = 106;
+            for (; size < 256; size <<= 1) {
+                val = val.shiftLeft(size - 1).add(x.shiftRight
+                    (xLenMod - (3*size)).divide(val));}
+
+            if (xAsDub > 4e254) { // 4e254 = 1<<845.77
+                int numOfNewtonSteps = 31 -
+                                       Integer.numberOfLeadingZeros(wantedPrecision / size)+1;
+
+                ////// Apply Starting Size ////////
+                int wantedSize = (wantedPrecision >> numOfNewtonSteps) + 2;
+                int needToShiftBy = size - wantedSize;
+                val = val.shiftRight(needToShiftBy);
+
+                size = wantedSize;
+                do {
+                    //////// Newton Plus Iteration ////////
+                    int shiftX = xLenMod - (3 * size);
+                    BigInteger valSqrd = val.multiply(val).shiftLeft(size - 1);
+                    BigInteger valSU = x.shiftRight(shiftX).subtract(valSqrd);
+                    val = val.shiftLeft(size).add(valSU.divide(val));
+                    size *= 2;
+                } while (size < wantedPrecision);
+            }
+            val = val.shiftRight(size - wantedPrecision);
+        }
+
+        // Detect a round ups. This function can be further optimized - see article.
+        // For a ~7% speed bump the following line can be removed but round-ups will occur.
+        if (val.multiply(val).compareTo(x) > 0)
+            val = val.subtract(BigInteger.ONE);
+
+        // Enabling the below will guarantee an error is stopped for larger numbers.
+        // Note: As of this writing, there are no known errors.
+        BigInteger tmp = val.multiply(val);
+        if (tmp.compareTo(x) > 0) {
+            System.out.println("val^2(" + val.multiply(val).toString()
+                               + ") ≥ x(" + x.toString()+")");
+            System.console().readLine();
+            //throw new Exception("Sqrt function had internal error - value too high");
+        }
+        if (tmp.add(val.shiftLeft(1)).add(BigInteger.ONE).compareTo(x) <= 0) {
+            System.out.println("(val+1)^2("
+                               + val.add(BigInteger.ONE).multiply(val.add(BigInteger.ONE)).toString()
+                               + ") ≥ x(" + x.toString() + ")");
+            System.console().readLine();
+            //throw new Exception("Sqrt function had internal error - value too low");
+        }
+
+        return val;
+    }
+}
@@ -0,0 +1,39 @@
+package com.baeldung.bigintegerroot;
+
+
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import com.baeldung.bigintegerroot.algorithms.Newton;
+import com.baeldung.bigintegerroot.algorithms.NewtonPlus;
+import com.google.common.math.BigIntegerMath;
+import java.math.BigInteger;
+import java.math.RoundingMode;
+import java.util.stream.Stream;
+import org.apache.commons.math3.util.Pair;
+import org.junit.jupiter.api.condition.EnabledForJreRange;
+import org.junit.jupiter.api.condition.JRE;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.ValueSource;
+
+class BigIntegerSquareRootUnitTest {
+
+    @ParameterizedTest
+    @ValueSource(strings = {
+        BigIntegerHolder.BIG_NUMBER,
+        BigIntegerHolder.VERY_BIG_NUMBER,
+        BigIntegerHolder.VERY_BIG_NUMBER
+    })
+    void squareRootTest(String number) {
+        final BigInteger bigInteger = new BigInteger(number);
+        final BigInteger javaRoot = bigInteger.sqrt();
+        final BigInteger guavaRoot = BigIntegerMath.sqrt(bigInteger, RoundingMode.DOWN);
+        final BigInteger newtonRoot = Newton.sqrt(bigInteger);
+        final BigInteger newtonPlusRoot = NewtonPlus.sqrt(bigInteger);
+
+        assertTrue(Stream.of(
+            new Pair<>(javaRoot, guavaRoot),
+            new Pair<>(guavaRoot, newtonRoot),
+            new Pair<>(newtonRoot, newtonPlusRoot)
+        ).allMatch(pair -> pair.getFirst().equals(pair.getSecond())));
+    }
+}
@@ -14,5 +14,6 @@ This module contains articles about working with the operating system (OS) in Ja
 - [How to Run a Shell Command in Java](http://www.baeldung.com/run-shell-command-in-java)
 - [Taking Screenshots Using Java](https://www.baeldung.com/java-taking-screenshots)
 - [Java Sound API – Capturing Microphone](https://www.baeldung.com/java-sound-api-capture-mic)
+- [How to Detect the Username Using Java](https://www.baeldung.com/java-get-username)

 This module uses Java 9, so make sure to have the JDK 9 installed to run it.
@@ -9,4 +9,5 @@
 - [Regular Expression: \z vs \Z Anchors in Java](https://www.baeldung.com/java-regular-expression-z-vs-z-anchors)
 - [Extract Text Between Square Brackets](https://www.baeldung.com/java-get-content-between-square-brackets)
 - [Get the Indexes of Regex Pattern Matches in Java](https://www.baeldung.com/java-indexes-regex-pattern-matches)
+- [Check if a String is Strictly Alphanumeric With Java](https://www.baeldung.com/java-check-string-contains-only-letters-numbers)
 - More articles: [[<-- prev]](/core-java-modules/core-java-regex)