Convert Byte Array to its Numeric Representation

core-java-modules/core-java-arrays-convert/pom.xml

@@ -19,6 +19,11 @@
             <artifactId>guava</artifactId>
             <version>${guava.version}</version>
         </dependency>
+        <dependency>
+            <groupId>org.apache.commons</groupId>
+            <artifactId>commons-lang3</artifactId>
+            <version>${commons-lang3.version}</version>
+        </dependency>
     </dependencies>
 
     <properties>

core-java-modules/core-java-arrays-convert/src/main/java/com/baeldung/array/conversions/ByteArrayToNumericRepresentation.java

@@ -0,0 +1,281 @@
+package com.baeldung.array.conversions;
+
+import com.google.common.primitives.Ints;
+import com.google.common.primitives.Longs;
+import org.apache.commons.lang3.ArrayUtils;
+import org.apache.commons.lang3.Conversion;
+
+import java.math.BigInteger;
+import java.nio.ByteBuffer;
+import java.util.Arrays;
+
+class ByteArrayToNumericRepresentation {
+
+    static int convertByteArrayToIntUsingShiftOperator(byte[] bytes) {
+        int value = 0;
+        for (byte b : bytes) {
+            value = (value << 8) + (b & 0xFF);
+        }
+        return value;
+    }
+
+    static byte[] convertIntToByteArrayUsingShiftOperator(int value) {
+        byte[] bytes = new byte[Integer.BYTES];
+        int length = bytes.length;
+        for (int i = 0; i < length; i++) {
+            bytes[length - i - 1] = (byte) (value & 0xFF);
+            value >>= 8;
+        }
+        return bytes;
+    }
+
+    static long convertByteArrayToLongUsingShiftOperator(byte[] bytes) {
+        long value = 0;
+        for (byte b : bytes) {
+            value <<= 8;
+            value |= (b & 0xFF);
+        }
+        return value;
+    }
+
+    static byte[] convertLongToByteArrayUsingShiftOperator(long value) {
+        byte[] bytes = new byte[Long.BYTES];
+        int length = bytes.length;
+        for (int i = 0; i < length; i++) {
+            bytes[length - i - 1] = (byte) (value & 0xFF);
+            value >>= 8;
+        }
+        return bytes;
+    }
+
+    static float convertByteArrayToFloatUsingShiftOperator(byte[] bytes) {
+        // convert bytes to int
+        int intValue = 0;
+        for (byte b : bytes) {
+            intValue = (intValue << 8) + (b & 0xFF);
+        }
+
+        // convert int to float
+        return Float.intBitsToFloat(intValue);
+    }
+
+    static byte[] convertFloatToByteArrayUsingShiftOperator(float value) {
+        // convert float to int
+        int intValue = Float.floatToIntBits(value);
+
+        // convert int to bytes
+        byte[] bytes = new byte[Float.BYTES];
+        int length = bytes.length;
+        for (int i = 0; i < length; i++) {
+            bytes[length - i - 1] = (byte) (intValue & 0xFF);
+            intValue >>= 8;
+        }
+        return bytes;
+    }
+
+    static double convertingByteArrayToDoubleUsingShiftOperator(byte[] bytes) {
+        long longValue = 0;
+        for (byte b : bytes) {
+            longValue = (longValue << 8) + (b & 0xFF);
+        }
+
+        return Double.longBitsToDouble(longValue);
+    }
+
+    static byte[] convertDoubleToByteArrayUsingShiftOperator(double value) {
+        long longValue = Double.doubleToLongBits(value);
+
+        byte[] bytes = new byte[Double.BYTES];
+        int length = bytes.length;
+        for (int i = 0; i < length; i++) {
+            bytes[length - i - 1] = (byte) (longValue & 0xFF);
+            longValue >>= 8;
+        }
+        return bytes;
+    }
+
+    static int convertByteArrayToIntUsingByteBuffer(byte[] bytes) {
+        ByteBuffer buffer = ByteBuffer.allocate(Integer.BYTES);
+        buffer.put(bytes);
+        buffer.rewind();
+        return buffer.getInt();
+    }
+
+    static byte[] convertIntToByteArrayUsingByteBuffer(int value) {
+        ByteBuffer buffer = ByteBuffer.allocate(Integer.BYTES);
+        buffer.putInt(value);
+        buffer.rewind();
+        return buffer.array();
+    }
+
+    static long convertByteArrayToLongUsingByteBuffer(byte[] bytes) {
+        ByteBuffer buffer = ByteBuffer.allocate(Long.BYTES);
+        buffer.put(bytes);
+        buffer.rewind();
+        return buffer.getLong();
+    }
+
+    static byte[] convertLongToByteArrayUsingByteBuffer(long value) {
+        ByteBuffer buffer = ByteBuffer.allocate(Long.BYTES);
+        buffer.putLong(value);
+        buffer.rewind();
+        return buffer.array();
+    }
+
+    static float convertByteArrayToFloatUsingByteBuffer(byte[] bytes) {
+        ByteBuffer buffer = ByteBuffer.allocate(Float.BYTES);
+        buffer.put(bytes);
+        buffer.rewind();
+        return buffer.getFloat();
+    }
+
+    static byte[] convertFloatToByteArrayUsingByteBuffer(float value) {
+        ByteBuffer buffer = ByteBuffer.allocate(Float.BYTES);
+        buffer.putFloat(value);
+        buffer.rewind();
+        return buffer.array();
+    }
+
+    static double convertByteArrayToDoubleUsingByteBuffer(byte[] bytes) {
+        ByteBuffer buffer = ByteBuffer.allocate(Double.BYTES);
+        buffer.put(bytes);
+        buffer.rewind();
+        return buffer.getDouble();
+    }
+
+    static byte[] convertDoubleToByteArrayUsingByteBuffer(double value) {
+        ByteBuffer buffer = ByteBuffer.allocate(Double.BYTES);
+        buffer.putDouble(value);
+        buffer.rewind();
+        return buffer.array();
+    }
+
+    static int convertByteArrayToIntUsingBigInteger(byte[] bytes) {
+        return new BigInteger(bytes).intValue();
+    }
+
+    static byte[] convertIntToByteArrayUsingBigInteger(int value) {
+        return BigInteger.valueOf(value).toByteArray();
+    }
+
+    static long convertByteArrayToLongUsingBigInteger(byte[] bytes) {
+        return new BigInteger(bytes).longValue();
+    }
+
+    static byte[] convertLongToByteArrayUsingBigInteger(long value) {
+        return BigInteger.valueOf(value).toByteArray();
+    }
+
+    static float convertByteArrayToFloatUsingBigInteger(byte[] bytes) {
+        int intValue = new BigInteger(bytes).intValue();
+        return Float.intBitsToFloat(intValue);
+    }
+
+    static byte[] convertFloatToByteArrayUsingBigInteger(float value) {
+        int intValue = Float.floatToIntBits(value);
+        return BigInteger.valueOf(intValue).toByteArray();
+    }
+
+    static double convertByteArrayToDoubleUsingBigInteger(byte[] bytes) {
+        long longValue = new BigInteger(bytes).longValue();
+        return Double.longBitsToDouble(longValue);
+    }
+
+    static byte[] convertDoubleToByteArrayUsingBigInteger(double value) {
+        long longValue = Double.doubleToLongBits(value);
+        return BigInteger.valueOf(longValue).toByteArray();
+    }
+
+    static int convertingByteArrayToIntUsingGuava(byte[] bytes) {
+        return Ints.fromByteArray(bytes);
+    }
+
+    static byte[] convertIntToByteArrayUsingGuava(int value) {
+        return Ints.toByteArray(value);
+    }
+
+    static long convertByteArrayToLongUsingGuava(byte[] bytes) {
+        return Longs.fromByteArray(bytes);
+    }
+
+    static byte[] convertLongToByteArrayUsingGuava(long value) {
+        return Longs.toByteArray(value);
+    }
+
+    static float convertByteArrayToFloatUsingGuava(byte[] bytes) {
+        int intValue = Ints.fromByteArray(bytes);
+        return Float.intBitsToFloat(intValue);
+    }
+
+    static byte[] convertFloatToByteArrayUsingGuava(float value) {
+        int intValue = Float.floatToIntBits(value);
+        return Ints.toByteArray(intValue);
+    }
+
+    static double convertByteArrayToDoubleUsingGuava(byte[] bytes) {
+        long longValue = Longs.fromByteArray(bytes);
+        return Double.longBitsToDouble(longValue);
+    }
+
+    static byte[] convertDoubleToByteArrayUsingGuava(double value) {
+        long longValue = Double.doubleToLongBits(value);
+        return Longs.toByteArray(longValue);
+    }
+
+    static int convertByteArrayToIntUsingCommonsLang(byte[] bytes) {
+        byte[] copyBytes = Arrays.copyOf(bytes, bytes.length);
+        ArrayUtils.reverse(copyBytes);
+        return Conversion.byteArrayToInt(copyBytes, 0, 0, 0, copyBytes.length);
+    }
+
+    static byte[] convertIntToByteArrayUsingCommonsLang(int value) {
+        byte[] bytes = new byte[Integer.BYTES];
+        Conversion.intToByteArray(value, 0, bytes, 0, bytes.length);
+        ArrayUtils.reverse(bytes);
+        return bytes;
+    }
+
+    static long convertByteArrayToLongUsingCommonsLang(byte[] bytes) {
+        byte[] copyBytes = Arrays.copyOf(bytes, bytes.length);
+        ArrayUtils.reverse(copyBytes);
+        return Conversion.byteArrayToLong(copyBytes, 0, 0, 0, copyBytes.length);
+    }
+
+    static byte[] convertLongToByteArrayUsingCommonsLang(long value) {
+        byte[] bytes = new byte[Long.BYTES];
+        Conversion.longToByteArray(value, 0, bytes, 0, bytes.length);
+        ArrayUtils.reverse(bytes);
+        return bytes;
+    }
+
+    static float convertByteArrayToFloatUsingCommonsLang(byte[] bytes) {
+        byte[] copyBytes = Arrays.copyOf(bytes, bytes.length);
+        ArrayUtils.reverse(copyBytes);
+        int intValue = Conversion.byteArrayToInt(copyBytes, 0, 0, 0, copyBytes.length);
+        return Float.intBitsToFloat(intValue);
+    }
+
+    static byte[] convertFloatToByteArrayUsingCommonsLang(float value) {
+        int intValue = Float.floatToIntBits(value);
+        byte[] bytes = new byte[Float.BYTES];
+        Conversion.intToByteArray(intValue, 0, bytes, 0, bytes.length);
+        ArrayUtils.reverse(bytes);
+        return bytes;
+    }
+
+    static double convertByteArrayToDoubleUsingCommonsLang(byte[] bytes) {
+        byte[] copyBytes = Arrays.copyOf(bytes, bytes.length);
+        ArrayUtils.reverse(copyBytes);
+        long longValue = Conversion.byteArrayToLong(copyBytes, 0, 0, 0, copyBytes.length);
+        return Double.longBitsToDouble(longValue);
+    }
+
+    static byte[] convertDoubleToByteArrayUsingCommonsLang(double value) {
+        long longValue = Double.doubleToLongBits(value);
+        byte[] bytes = new byte[Long.BYTES];
+        Conversion.longToByteArray(longValue, 0, bytes, 0, bytes.length);
+        ArrayUtils.reverse(bytes);
+        return bytes;
+    }
+
+}