Cast from string to boolean java

3 ways to convert String to Boolean in Java? Examples

Hello guys, if you ar wondering how to convert a String object to boolean value in Java then don’t sweat there are multiple ways to convert a String to Boolean class or boolean value in Java. For Example, ou can convert a String object to a Boolean object or boolean primitive by using the Boolean.valueOf() and Boolean.parseBoolean() method. The steps are similar rot converting to String to other data types like String to Integer and String to Long. You can use the valueOf() method to convert String to Boolean object and parseBoolean() method to convert a given string to a boolean primitive value. Internally, valueOf() also uses parseBoolean() for parsing String but on top of that it also provides caching e.g. it can return Boolean.TRUE and Boolean.FALSE cached value for «true» and » false» strings.

In fact, B oolean.TRUE is returned only when String is equal to true ignoring cases like «True», «true», «TRUE» will evaluate into boolean true, hence Boolean.TRUE will be returned. For strings like «Yes», Boolean.FALSE will be returned. We’ll discuss the rules of String to boolean conversion in the next section.

Rules of String to Boolean Conversion in Java

The parsing logic is encapsulated in the parseBoolean() method which is also leveraged or used by valueOf() . According to this logic, the parseBoolean() method returns true if the given string is not null and equal to the true ignoring case and false otherwise.

For example, «true», «True», and «TRUE» all will return Boolean.TRUE value but «Yes» will return Boolean.FALSE . Similarly, «false», «False», or «FALSE» will also return Boolean.FALSE

Boolean.parseBoolean("True") returns true. Boolean.parseBoolean("TRUE") returns true. Boolean.parseBoolean("true") returns true. Boolean.parseBoolean("yes") returns false. Boolean.parseBoolean("y") returns false. Boolean.parseBoolean("no") returns false. Boolean.parseBoolean("false") returns false. Boolean.parseBoolean("False") returns false. Boolean.parseBoolean("FALSE") returns false.

If you want to know more about how to convert one data type to others in Java, The Complete Java Masterclass is a good resource to learn it in depth.

Boolean.parseBoolean() Example

The parseBoolean() method is similar to the parseInt() method and it returns a primitive boolean value after parsing the given String. It returns a boolean value, true or false based upon the rules given above.

It compares String by ignoring case and only return true if String matches true after ignoring cases.

Boolean.parseBoolean("True") returns true. Boolean.parseBoolean("TRUE") returns true. Boolean.parseBoolean("true") returns true. Boolean.parseBoolean("yes") returns false.

You should use this method if you need a primitive boolean value.

Boolean.valueOf() Example

This method should be used to convert a String object to a Boolean object in Java. It leverages the parsing logic of the parseooleBan() method but it also uses the Flyweight design pattern to cache frequently used values and returns them.

Since boolean can either be true or false, it just uses two Boolean instances, Boolean.TRUE and Boolean.FALSE , for all String to Boolean conversion, which drastically reduces the number of objects and causes less overhead for the Garbage collector.

Here are some examples of converting String to Boolean using the valueOf() method:

Boolean.valueOf("True") returns Boolean.TRUE. Boolean.valueOf("TRUE") returns Boolean.TRUE. Boolean.valueOf("true") returns Boolean.TRUE. Boolean.valueOf("yes") returns Boolean.FALSE. Boolean.valueOf("y") returns Boolean.FALSE. Boolean.valueOf("no") returns Boolean.FALSE. Boolean.valueOf("false") returns Boolean.FALSE. Boolean.valueOf("False") returns Boolean.FALSE. Boolean.valueOf("FALSE") returns Boolean.FALSE.

You should use this method if you need a Boolean object from String rather than a boolean primitive value. If you want to know more about primitive data types in Java then these best LinkedIn Learning Java courses are a good place to start with.

Java Program to convert String to Boolean with Example

Here is your complete Java program, which you can copy and paste in your Eclipse IDE and run. This program accepts user input as String and tries to convert it to a boolean. If successful, it prints that value into the console, otherwise, it throws an error.

package tool; import java.util.Scanner; /** * * A simple Java Program to convert String to Boolean or boolean data type. */ public class Hello < public static void main(String[] args) < System.out.println("Please enter a boolean String e.g. true or false"); Scanner sc = new Scanner(System.in); String input = sc.next(); boolean b = Boolean.valueOf(input); System.out.println("converted boolean value from String using valueOf: " + b); boolean value = Boolean.parseBoolean(input); System.out .println("converted boolean value from String using parseBoolean: " + value); sc.close(); // you can also use constructor but that is not encouraged by Effective Java Boolean bool = new Boolean(input); System.out .println("converted boolean value from String using constructor: " + bool); > > Output Please enter a boolean String e.g. true or false true converted boolean value from String using valueOf: true converted boolean value from String using parseBoolean: true converted boolean value from String using constructor: true

Here is the summary of all three methods to convert String to Boolean in Java:

Important points about String to boolean conversion

5.1 Even though you can also use the constructor of java.lang.Boolean class to convert String to a Boolean object, it’s not encouraged by Effective Java of Joshua Bloch, which advice preferring static factory methods like valueOf() to take advantage of caching they offer.

5.2. The parsing rules i.e. how the string is actually converted into a boolean value are written in parseBoolean() method.

5.3 Both valueOf() and parseBoolean() method belongs to java.lang.Boolean class.

5.4. The valueOf() method returns either the Boolean.TRUE or Boolean.FALSE object, which is shared by all boolean values converted.

That’s all about how to convert String to Boolean or boolean in Java. As I said, you can use either Boolean.valueOf() , a static factory method, or the parseBoolean() method for this conversion. The rule of thumb is to prefer valueOf() if you need a Boolean object and parseBoolean() if you need a boolean primitive value.

• How to convert double to long in Java? (example)
• How to convert Array to String in Java (read here)
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• How to convert String to int in Java? (example)
• Best way to Convert Numbers to String in Java (read here)
• How to convert Enum to String in Java (see here)
• How to convert String to Integer in Java (read here)
• How to convert decimal to binary numbers in Java (see here)
• Converting List to Set in Java (check here)
• How to convert hexadecimal to decimal, binary, and octal in Java (see here)

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Java String to boolean Conversion with examples

In this guide, we will see how to convert a String to a boolean with the help of examples.

When converting a String to a boolean value, if the string contains the value “true” (case doesn’t matter) then the boolean value after the conversion would be true, if the string contains any other value other than “true” then the converted boolean value would be “false”.

Java String to boolean conversion using Boolean.parseBoolean() method example

Here we have three Strings str1, str2 and str3 and we are converting them into boolean value using the Boolean.parseBoolean() method, this method accepts String as an argument and returns boolean value true or false. If the value of the string is “true” (in any case uppercase, lowercase or mixed) then this method returns true, else it returns false.

Output:

Java String to boolean using Boolean.valueOf() example

Here we will see another method which we can use for string to boolean conversion. Similar to Boolean.parseBoolean() method, the Boolean.valueOf() method accepts string as an argument and returns a boolean value true or false.

Output:

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How to convert a String to boolean in Java

We can convert a String to a primitive boolean using the Boolean.parseBoolean method or to a wrapped Boolean class using the Boolean.valueOf .

Info: By default the converted String will only convert «true» and «false» to the correct representation of a Boolean . Every other value passed to the Boolean.parseBoolean or Boolean.valueOf methods results in «false». If you want to convert a custom value like: «1». to a boolean you can do the following:

String isNumberBoolean = "1"; Boolean isBoolean = "1".equals(isNumberBoolean);

Convert String to boolean using Boolean.parseBoolean

The Boolean.parseBoolean method is used to convert a String to primitive boolean .

String isBoolean = "true"; boolean convertedIsBoolean = Boolean.parseBoolean(isBoolean); System.out.println("Convert String to boolean: " + convertedIsBoolean); String isNumberBoolean = "1"; boolean convertedIsNumberBoolean = Boolean.parseBoolean(isNumberBoolean); System.out.println("Convert String Number to boolean: " + convertedIsNumberBoolean); String isInvalidBoolean = "-abc"; boolean convertedIsInvalidBoolean = Boolean.parseBoolean(isInvalidBoolean); System.out.println("Convert String string to boolean: " + convertedIsInvalidBoolean);

The previous will generate the following output.

Convert String to boolean: true Convert String Number to boolean: false Convert String string to boolean: false

Convert String to Boolean using Boolean.valueOf

The Boolean.valueOf method is used to convert a String to a wrapped Boolean .

String isBoolean = "true"; Boolean convertedIsBoolean = Boolean.valueOf(isBoolean); System.out.println("Convert String to boolean: " + convertedIsBoolean); String isNumberBoolean = "1"; Boolean convertedIsNumberBoolean = Boolean.valueOf(isNumberBoolean); System.out.println("Convert String number to boolean: " + convertedIsNumberBoolean); String isInvalidBoolean = "-abc"; Boolean convertedIsInvalidBoolean = Boolean.valueOf(isInvalidBoolean); System.out.println("Convert String string to boolean: " + convertedIsInvalidBoolean);

The previous will generate the following output.

Convert String to boolean: true Convert String number to boolean: false Convert String string to boolean: false

References

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Convert a String to a Boolean value in Java

This post will discuss how to convert a string to Boolean in Java. In other words, return the Boolean value represented by a specified string.

1. Using Boolean.valueOf() method

The simplest solution is to use the Boolean.valueOf() , which returns Boolean.TRUE if the specified string is equal to “true”, case ignored.

Output:

true
false

2. Using Boolean.parseBoolean() method

Another plausible way to get the boolean value of a string is to use the Boolean.parseBoolean() method, which returns primitive boolean and offers better performance than Boolean.valueOf() method.

Output:

true
false

3. Using String.equalsIgnoreCase() method

The final approach is to use the String.equalsIgnoreCase() and compares the specified string with the string “true”, as shown below:

Output:

true
false

All three approach discussed above are different but are related. Internally, Boolean.valueOf() method makes call to Boolean.parseBoolean() method, which in turn uses String.equalsIgnoreCase() .

The problem with the above-mentioned methods is that they all return false when the specified string is null or is not equal to the string “true”, case ignored. One solution is to ensure that the specified string is valid or not in advance and returns a null when invalid.

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