Remove Insignificant Zeros From a Numeric String Example

Mary ZhengFebruary 19th, 2025Last Updated: February 17th, 2025

0 107 4 minutes read

1. Introduction

Insignificant zeros refer to zeros that don’t affect the value of the number. In this example, I will delete leading trailing zeros from a numeric string with the following methods:

public String java.lang.String.replaceFirst(String regex, String replacement) – replaces the first substring of this string that matches the given regular expression pattern
public String java.lang.String.replaceAll(String regex, String replacement) – replaces each substring of this string that matches the given regular expression pattern.
public final String java.text.NumberFormat.format(double number) – formats the number based on the format.
public BigDecimal java.math.BigDecimal.stripTrailingZeros()- returns a BigDecimal which is numerically equal to this one but with any trailing zeros removed from the representation.

2. Setup

In this step, I will create a Java project in Eclipse IDE with the JUnit5 library. The RemoveInsignificantZerosBase has three children that implement removeInsignificantZero method with different approaches.

2.1 Delete Leading Trailing Zeros Base Class

In this step, I will create a RemoveInsignificantZerosBase.java that includes several constants and a removeInsignificantZero method to remove insignificant zeros from a numeric string.

RemoveInsignificantZerosBase.java

package org.zheng.demo;
 
public abstract class RemoveInsignificantZerosBase {
 
    protected static final String EMPTY = "";
    protected static final String DOT = ".";
 
    protected RemoveInsignificantZerosBase() {
        super();
    }
 
    public abstract String removeInsignificantZero(final String rawNumStr);
 
}

Line 12: defines an abstract method removeInsignificantZero to delete the leading trailing zeros from a numeric string.

2.2 RemoveInsignificantZerosBaseTest

In this step, I will create a RemoveInsignificantZerosBaseTest.java that verifies a numeric string with leading and trailing zeros removed.

RemoveInsignificantZerosBaseTest.java

package org.zheng.demo;
 
import static org.junit.jupiter.api.Assertions.*;
 
import org.junit.jupiter.api.Test;
 
abstract class RemoveInsignificantZerosBaseTest {
 
    protected RemoveInsignificantZerosBase testClass;
 
    private static final String DECIMAL_NUMBER = "123.45";
    private static final String LEADING_TRAILIG_ZERO_INT = "000123.000";
    private static final String LEADING_TRAILING_DECIMAL = "000123.4500";
    private static final String LEADING_ZERO_DECIMAL = "000123.45";
    private static final String LEADING_ZERO_INT = "000123";
    private static final String NUMBER = "123";
    private static final String NUMBER_WITH_ZERO = "1230";
    private static final String TAILING_INT = "123.000";
 
    @Test
    void test_removeInsignificantZero_leading_trailingZero_decimal() {
        assertEquals(DECIMAL_NUMBER, testClass.removeInsignificantZero(LEADING_TRAILING_DECIMAL));
    }
 
    @Test
    void test_removeInsignificantZero_leading_trailingZero_int() {
        assertEquals(NUMBER, testClass.removeInsignificantZero(LEADING_TRAILIG_ZERO_INT));
    }
 
    @Test
    void test_removeInsignificantZero_leadingZero_decimal() {
        assertEquals(DECIMAL_NUMBER, testClass.removeInsignificantZero(LEADING_ZERO_DECIMAL));
    }
 
    @Test
    void test_removeInsignificantZero_leadingZero_int() {
        assertEquals(NUMBER, testClass.removeInsignificantZero(LEADING_ZERO_INT));
    }
 
    @Test
    void test_removeInsignificantZero_nochange() {
        assertEquals(NUMBER, testClass.removeInsignificantZero(NUMBER));
    }
 
    @Test
    void test_removeInsignificantZero_nochange_int() {
        assertEquals(NUMBER_WITH_ZERO, testClass.removeInsignificantZero(NUMBER_WITH_ZERO));
    }
 
    @Test
    void test_removeInsignificantZero_trailing() {
        assertEquals(NUMBER, testClass.removeInsignificantZero(TAILING_INT));
    }
 
    @Test
    void test_removeInsignificantZero_allZero() {
        assertEquals("0", testClass.removeInsignificantZero("0000.000"));
 
    }
 
}

Line 11: defines a DECIMAL_NUMBER variable without any leading trailing zeros with the value of "123.45".
Line 12: defines a LEADING_TRAILIG_ZERO_INT variable with both leading and trailing zeros with the value of "000123.000".
Line 13: defines a LEADING_TRAILING_DECIMAL variable with both leading and trailing zeros with the value of "000123.45000".
Line 14: defines a LEADING_ZERO_DECIMAL variable with leading zeros with the value of "000123.45".
Line 15: defines a LEADING_ZERO_INT variable with leading zeros with the value of "000123".
Line 16: defines a NUMBER variable with both leading and trailing zeros with the value of "123".
Line 17: defines a NUMBER_WITH_ZERO variable with a significant zero with the value of "1230".
Line 18: defines a TAILING_INT variable with trailing zeros with the value of "123.000".
Line 57: verified the special case – the zeros string is trimmed to "0".

3. Delete Leading Trailing Zeros via String.replaceAll

In this step, I will create a RemoveZeroViaRegularExpress.java class to delete insignificant zeros from a numeric string via the replaceAll and replaceFirst methods.

RemoveZeroViaRegularExpress.java

package org.zheng.demo;
 
public class RemoveZeroViaRegularExpress extends RemoveInsignificantZerosBase {
 
    protected static final String LEADING_ZERO_REGEX = "^0+(?!$)";
    protected static final String TRAILING_ZERO_REGEX = "\\.?0+$";
 
    public String removeInsignificantZero(final String rawNumStr) {
        int docIndex = rawNumStr.indexOf(DOT);
        String result = rawNumStr.replaceFirst(LEADING_ZERO_REGEX, EMPTY);
 
        if (docIndex > -1) {
            result = result.replaceAll(TRAILING_ZERO_REGEX, EMPTY);
        }
 
        return handleEdgeCases(result);
 
    }
 
    private String handleEdgeCases(final String formatted) {
        if (EMPTY.endsWith(formatted)) {
            return "0";
        }
 
        if (formatted.startsWith(DOT)) {
            return "0".concat(formatted);
        }
 
        return formatted;
    }
 
}

Line 5 & 6: define the regular expression for leading and trailing zeros.
Line 9: check if the rawNumStr argument contains the decimal point(.).
Line 10: remove any leading zeros with the regular expression pattern: LEADING_ZERO_REGEX.
Line 13: remove the trailing zeros after the decimal point.
Line 20: handles the special case when the rawNumStr argument only contains zeros.

3.1 RemoveZeroViaRegularExpressTest

In this step, I will create a RemoveZeroViaRegularExpressTest.java class to verify.

RemoveZeroViaRegularExpress.java

package org.zheng.demo;
 
import org.junit.jupiter.api.BeforeEach;
 
class RemoveZeroViaRegularExpressTest extends RemoveInsignificantZerosBaseTest {
 
    @BeforeEach
    void setup() {
        testClass = new RemoveZeroViaRegularExpress();
 
    }
}

Line 9: assign a new object of RemoveZeroViaRegularExpress to the testClass variable.

4. Delete Insignificant Zeros via DecimalFormat

In this step, I will create a RemoveZeroViaDecimalFormat.java class to delete insignificant zeros from a numeric string via the parseDouble and format methods.

RemoveZeroViaDecimalFormat

package org.zheng.demo;
 
import java.text.DecimalFormat;
 
public class RemoveZeroViaDecimalFormat extends RemoveInsignificantZerosBase {
 
    private static final String NUMBER_PATTERN = "#.##";
 
    public String removeInsignificantZero(final String rawNumStr) {
 
        // Define a DecimalFormat pattern to remove trailing zeros
        DecimalFormat decimalFormat = new DecimalFormat(NUMBER_PATTERN);
 
        // Parse the input string to a number (double)
        double number = Double.parseDouble(rawNumStr);
 
        // Format the number using DecimalFormat to remove trailing zeros
        return decimalFormat.format(number);
 
    }
 
}

Line 7: define a decimal format string NUMBER_PATTERN with "#.##".
Line 15: convert the rawNumStr to double via the parseDouble method.
Line 18: return the string format of the double value via the format method.

4.1 RemoveZeroViaDecimalFormatTest

In this step, I will create a RemoveZeroViaFormatTest.java class.

RemoveZeroViaDecimalFormatTest.java

package org.zheng.demo;
 
import org.junit.jupiter.api.BeforeEach;
 
class RemoveZeroViaDecimalFormatTest extends RemoveInsignificantZerosBaseTest {
 
    @BeforeEach
    void setup() {
        testClass = new RemoveZeroViaDecimalFormat();
 
    }
}

5. Delete Insignificant Zeros via BigDecimal

In this step, I will create a RemoveZeroViaBigDecimal.java class to delete insignificant zeros from a numeric string via the stripTrailingZeros and toPlainString methods.

RemoveZeroViaBigDecimal.java

package org.zheng.demo;
 
import java.math.BigDecimal;
 
public class RemoveZeroViaBigDecimal extends RemoveInsignificantZerosBase {
 
    public String removeInsignificantZero(final String rawNumStr) {
 
        // Create a BigDecimal from the input string
        BigDecimal bigDecimal = new BigDecimal(rawNumStr);
 
        // Use stripTrailingZeros to remove unnecessary zeros
        BigDecimal strippedDecimal = bigDecimal.stripTrailingZeros();
 
        // Convert the result back to a String
        return strippedDecimal.toPlainString();
 
    }
 
}

Line 10: create a new BigDecimal object from the rawNumStr argument.
Line 13: remove insignificant zeros via the stripTrailingZeros method.
Line 16: return the string format via the toPlainString method.

5.1 RemoveZeroViaBigDecimalTest

In this step, I will create a RemoveZeroViaBigDecimalTest.java class.

RemoveZeroViaBigDecimalTest.java

package org.zheng.demo;
 
import org.junit.jupiter.api.BeforeEach;
 
class RemoveZeroViaBigDecimalTest extends RemoveInsignificantZerosBaseTest {
 
    @BeforeEach
    void setup() {
        testClass = new RemoveZeroViaBigDecimal();
 
    }
}

6. Conclusion

In this example, I created several classes to delete leading trailing zeros from a numeric string using java.lang.String, java.text.NumberFormat, and java.math.BigDecimal classes’ methods. I also verified with Junit5 test classes. As Figure 1 shows, the RemoveZeroViaRegularExpress approach performs best as it does not need to convert to the other object. However, the logic is a bit complex.

7. Download

This was an example of a Java project that deletes leading trailing zeros from a numeric string.

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You can download the full source code of this example here: Remove Insignificant Zeros From a Numeric String Example

Remove Insignificant Zeros From a Numeric String Example

1. Introduction

2. Setup

2.1 Delete Leading Trailing Zeros Base Class

2.2 RemoveInsignificantZerosBaseTest

3. Delete Leading Trailing Zeros via String.replaceAll

3.1 RemoveZeroViaRegularExpressTest

4. Delete Insignificant Zeros via DecimalFormat

4.1 RemoveZeroViaDecimalFormatTest

5. Delete Insignificant Zeros via BigDecimal

5.1 RemoveZeroViaBigDecimalTest

6. Conclusion

7. Download

Thank you!

Mary Zheng

Thank you!

1. Introduction

2. Setup

2.1 Delete Leading Trailing Zeros Base Class

2.2 RemoveInsignificantZerosBaseTest

3. Delete Leading Trailing Zeros via String.replaceAll

3.1 RemoveZeroViaRegularExpressTest

4. Delete Insignificant Zeros via DecimalFormat

4.1 RemoveZeroViaDecimalFormatTest

5. Delete Insignificant Zeros via BigDecimal

5.1 RemoveZeroViaBigDecimalTest

6. Conclusion

7. Download

Thank you!

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