BAEL-4814 Bitmasking in Java with Bitwise Operators (#11069)

2021-07-26 10:58:35 +02:00 · 2021-07-26 10:58:35 +02:00 · 54f85ac6cd
parent dd50f5e80b
commit 54f85ac6cd
1 changed files with 120 additions and 0 deletions
--- a/core-java-modules/core-java-lang-operators-2/src/test/java/com/baeldung/oroperators/BitmaskingUnitTest.java
+++ b/core-java-modules/core-java-lang-operators-2/src/test/java/com/baeldung/oroperators/BitmaskingUnitTest.java
@ -0,0 +1,120 @@
+package com.baeldung.oroperators;
+
+import org.junit.Test;
+
+import java.util.Arrays;
+
+import static org.junit.Assert.*;
+
+public class BitmaskingUnitTest {
+
+    @Test
+    public void givenIntegerShouldPrintBinaryRepresentation() {
+        // given
+        int intRepresentation = 1094795523;
+
+        // expected
+        String stringRepresentation = getStringRepresentation(intRepresentation);
+        assertEquals(stringRepresentation, "01000001010000010100000100000011");
+    }
+
+    private String getStringRepresentation(int intRepresentation) {
+        String binaryString = Integer.toBinaryString(intRepresentation);
+        return padWithZeros(binaryString);
+    }
+
+    private String padWithZeros(String binaryString) {
+        return String.format("%" + 32 + "s", binaryString).replace(' ', '0');
+    }
+
+    @Test
+    public void givenBinaryRepresentationShouldReturnNumber() {
+        // given
+        String stringRepresentation = "01000001010000010100000100000011";
+
+        // expected
+        int intRepresentation = Integer.parseUnsignedInt(stringRepresentation, 2);
+        assertEquals(intRepresentation, 1094795523);
+    }
+
+    @Test
+    public void givenBinaryRepresentationShouldReturnCharacter() {
+        // given
+        String stringRepresentation = "010000010100000101000001";
+
+        // expected
+        assertEquals(binaryToText(stringRepresentation), "AAA");
+    }
+
+    @Test
+    public void givenIntAndPositionNumberShouldReturnBitValue() {
+        // given
+        String stringRepresentation = "010000010100000101000001000000011";
+        int intRepresentation = Integer.parseUnsignedInt(stringRepresentation, 2);
+
+        // when
+        boolean value1 = extractValueAtPosition(intRepresentation, 1);
+        boolean value2 = extractValueAtPosition(intRepresentation, 2);
+        boolean value3 = extractValueAtPosition(intRepresentation, 3);
+
+        // then
+        assertTrue(value1);
+        assertTrue(value2);
+        assertFalse(value3);
+
+    }
+
+    @Test
+    public void givenIntegerShouldExtractLastThreeBytes() {
+        // given
+        int intRepresentation = 1094795523;
+
+        // when
+        int lastThreeBites = intRepresentation >> 8;
+
+        // expected
+        String stringRepresentation = getStringRepresentation(lastThreeBites);
+        assertEquals(stringRepresentation, "00000000010000010100000101000001");
+        assertEquals(binaryToText(stringRepresentation), "AAA");
+    }
+
+    @Test
+    public void givenIntegerShouldApplyMask() {
+        // given
+        int intRepresentation = Integer.parseUnsignedInt("00000000010000010100000101000001", 2);
+        int mask = Integer.parseUnsignedInt("00000000000000000000000000000011", 2);
+        int mask2 = Integer.parseUnsignedInt("00000000000000000000000000000001", 2);
+
+        // when
+        int masked = intRepresentation & mask;
+        int masked2 = intRepresentation & mask2;
+
+        // expected
+        assertEquals(getStringRepresentation(masked), "00000000000000000000000000000001");
+        assertEquals(getStringRepresentation(masked2), "00000000000000000000000000000001");
+        assertNotEquals(masked, mask);
+        assertEquals(masked2, mask2);
+        assertFalse((intRepresentation & mask) == mask);
+    }
+
+    private boolean extractValueAtPosition(int intRepresentation, int position) {
+        String mask = getStringRepresentation(1 << (position - 1));
+        System.out.println(getStringRepresentation(intRepresentation));
+        System.out.println(mask);
+        System.out.println("-------------------------------- &");
+        System.out.println(getStringRepresentation((intRepresentation) & (1 << (position - 1))));
+        System.out.println();
+        return ((intRepresentation) & (1 << (position - 1))) != 0;
+    }
+
+    private static String binaryToText(String stringRepresentation) {
+        return Arrays.stream(stringRepresentation.split("(?<=\\G.{8})"))
+                .filter(eightBits -> !eightBits.equals("00000000"))
+                .map(eightBits -> (char)Integer.parseInt(eightBits, 2))
+                .collect(
+                        StringBuilder::new,
+                        StringBuilder::append,
+                        StringBuilder::append
+                ).toString();
+    }
+}