Merge pull request #9344 from marcinkrykowski/number-formatting-java
Add Format Number implementation and tests
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package com.baeldung.formatNumber;
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import java.math.BigDecimal;
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import java.math.RoundingMode;
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import java.text.DecimalFormat;
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import java.text.NumberFormat;
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import java.util.Locale;
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public class FormatNumber {
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public static double withBigDecimal(double value, int places) {
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if (places < 0)
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throw new IllegalArgumentException();
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BigDecimal bigDecimal = new BigDecimal(value);
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bigDecimal = bigDecimal.setScale(places, RoundingMode.HALF_UP);
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return bigDecimal.doubleValue();
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}
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public static double withMathRound(double value, int places) {
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double scale = Math.pow(10, places);
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return Math.round(value * scale) / scale;
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}
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public static double withDecimalFormatPattern(double value, int places) {
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DecimalFormat df2 = new DecimalFormat("#,###,###,##0.00");
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DecimalFormat df3 = new DecimalFormat("#,###,###,##0.000");
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if (places == 2)
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return new Double(df2.format(value));
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else if (places == 3)
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return new Double(df3.format(value));
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else
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throw new IllegalArgumentException();
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}
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public static double withDecimalFormatLocal(double value) {
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DecimalFormat df = (DecimalFormat) NumberFormat.getNumberInstance(Locale.getDefault());
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return new Double(df.format(value));
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}
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public static String withStringFormat(double value, int places) {
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return String.format("%." + places + "f", value);
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}
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public static String byPaddingZeros(int value, int paddingLength) {
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return String.format("%0" + paddingLength + "d", value);
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}
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public static double withTwoDecimalPlaces(double value) {
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DecimalFormat df = new DecimalFormat("#.00");
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return new Double(df.format(value));
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}
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public static String withLargeIntegers(double value) {
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DecimalFormat df = new DecimalFormat("###,###,###");
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return df.format(value);
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}
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public static String forPercentages(double value, Locale localisation) {
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NumberFormat nf = NumberFormat.getPercentInstance(localisation);
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return nf.format(value);
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}
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public static String currencyWithChosenLocalisation(double value, Locale localisation) {
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NumberFormat nf = NumberFormat.getCurrencyInstance(localisation);
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return nf.format(value);
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}
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public static String currencyWithDefaultLocalisation(double value) {
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NumberFormat nf = NumberFormat.getCurrencyInstance();
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return nf.format(value);
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}
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}
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package com.baeldung.formatNumber;
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import org.junit.Test;
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import java.util.Locale;
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import static com.baeldung.formatNumber.FormatNumber.*;
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import static org.assertj.core.api.Assertions.*;
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public class FormatNumberUnitTest {
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private static final double D = 4.2352989244d;
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private static final double F = 8.6994540927d;
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@Test
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public void givenDecimalNumber_whenFormatNumberWithBigDecimal_thenGetExpectedResult() {
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assertThat(withBigDecimal(D, 2)).isEqualTo(4.24);
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assertThat(withBigDecimal(D, 3)).isEqualTo(4.235);
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assertThat(withBigDecimal(F, 2)).isEqualTo(8.7);
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assertThat(withBigDecimal(F, 3)).isEqualTo(8.699);
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}
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@Test
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public void givenDecimalNumber_whenFormatNumberWithDecimalFormat_thenGetExpectedResult() {
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assertThat(withDecimalFormatLocal(D)).isEqualTo(4.235);
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assertThat(withDecimalFormatLocal(F)).isEqualTo(8.699);
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assertThat(withDecimalFormatPattern(D, 2)).isEqualTo(4.24);
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assertThat(withDecimalFormatPattern(D, 3)).isEqualTo(4.235);
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assertThat(withDecimalFormatPattern(F, 2)).isEqualTo(8.7);
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assertThat(withDecimalFormatPattern(F, 3)).isEqualTo(8.699);
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}
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@Test
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public void givenDecimalNumber_whenFormatNumberWithStringFormat_thenGetExpectedResult() {
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assertThat(withStringFormat(D, 2)).isEqualTo("4.24");
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assertThat(withStringFormat(D, 3)).isEqualTo("4.235");
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assertThat(withStringFormat(F, 2)).isEqualTo("8.70");
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assertThat(withStringFormat(F, 3)).isEqualTo("8.699");
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}
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@Test
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public void givenDecimalNumber_whenFormatNumberWithMathRound_thenGetExpectedResult() {
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assertThat(withMathRound(D, 2)).isEqualTo(4.24);
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assertThat(withMathRound(D, 3)).isEqualTo(4.235);
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assertThat(withMathRound(F, 2)).isEqualTo(8.7);
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assertThat(withMathRound(F, 3)).isEqualTo(8.699);
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}
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@Test
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public void givenIntegerNumber_whenFormatNumberByPaddingOutZeros_thenGetExpectedResult() {
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int value = 1;
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assertThat(byPaddingZeros(value, 3)).isEqualTo("001");
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}
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@Test
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public void givenIntegerNumber_whenFormatNumberWithTwoDecimalPlaces_thenGetExpectedResult() {
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int value = 12;
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assertThat(withTwoDecimalPlaces(value)).isEqualTo(12.00);
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}
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@Test
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public void givenIntegerNumber_whenFormatNumberWithLargeIntegers_thenGetExpectedResult() {
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int value = 123456789;
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assertThat(withLargeIntegers(value)).isEqualTo("123,456,789");
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}
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@Test
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public void givenDecimalNumber_whenFormatNumberForPercentages_thenGetExpectedResult() {
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double value = 25f / 100f;
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assertThat(forPercentages(value, new Locale("en", "US"))).isEqualTo("25%");
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assertThat(forPercentages(value, new Locale("pl", "PL"))).isEqualTo("25%");
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}
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@Test
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public void givenCurrency_whenFormatNumberCurrencyWithChosenLocalisation_thenGetExpectedResult() {
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double value = 23_500;
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assertThat(currencyWithChosenLocalisation(value, new Locale("en", "US"))).isEqualTo("$23,500.00");
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assertThat(currencyWithChosenLocalisation(value, new Locale("zh", "CN"))).isEqualTo("¥23,500.00");
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assertThat(currencyWithChosenLocalisation(value, new Locale("pl", "PL"))).isEqualTo("23 500 zł");
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}
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}
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