In Java, we can use Double.parseDouble() to convert a String to double

1. Double.parseDouble()

Example to convert a String 3.142 to an primitive double.


	String str = "3.142";
	double pi = Double.parseDouble(str);
	System.out.println(pi);

Output


3.142

2. Double.valueOf()

Example to convert a String 3.142 to an Double object.


	String str = "3.142";
	Double pi = Double.valueOf(str);
	System.out.println(pi);

Output


3.142
Note
In summary, Double.parseDouble(String) returns a primitive double; while Double.valueOf(String) returns a new Double object.

3. NumberFormatException

If the string is not a parsable double, a NumberFormatException will be thrown.


	String str = "120,000";
	double salary = Double.parseDouble(str);
	System.out.println(salary);

Output


Exception in thread "main" java.lang.NumberFormatException: For input string: "120,000"
	at java.base/jdk.internal.math.FloatingDecimal.readJavaFormatString(FloatingDecimal.java:2054)
	at java.base/jdk.internal.math.FloatingDecimal.parseDouble(FloatingDecimal.java:110)
	at java.base/java.lang.Double.parseDouble(Double.java:549)
	at com.mkyong.App1.main(App1.java:9)

To fix it, replace , with a .


	DecimalFormat df = new DecimalFormat("0.00");
	
	String str = "120,000";
	double salary = Double.parseDouble(str.replace(",", "."));

	System.out.println(salary);
	System.out.println(df.format(salary));

Output


120.0
120.00

4. 12,000,000?

Try NumberFormat to parse the String and returns back a double.

StringToDouble.java

package com.mkyong;

import java.text.DecimalFormat;
import java.text.NumberFormat;
import java.text.ParseException;

public class StringToDouble {

    private static final DecimalFormat df = new DecimalFormat("0.00");

    public static void main(String[] args) throws ParseException {

        String str = "12,000,000";

        NumberFormat format = NumberFormat.getInstance();
        Number parse = format.parse(str);

        System.out.println(parse);

        double salary = parse.doubleValue();

        System.out.println(salary);
        System.out.println(df.format(salary));

    }

}

Output


12000000
1.2E7
12000000.00

References