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

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mdabrowski-eu 2021-07-26 10:58:35 +02:00 committed by GitHub
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commit 54f85ac6cd
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core-java-modules/core-java-lang-operators-2/src/test/java/com/baeldung/oroperators/BitmaskingUnitTest.java Normal file
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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();
}
}