Java trim() : Cleanest way to check null string before trimming?-CodePudding

I use trim() method in order to trim leading and trailing whitespaces in some of the string field.

siteRequest.getName().trim();

However, when string field is null, it throws exception as expected. I can check the values before trimming as shown below:

siteRequest.getName() ? siteRequest.getName() : siteRequest.getName().trim();

However, if it is possible I would prefer a cleaner way so that several people had already faced this problem. Any suggestion with a smarter approach?

CodePudding user response：

I like the idea from @Sebastiaan van den Broek but would prefer not to use the library and therefore look up its implementation:

// Trim
//-----------------------------------------------------------------------
/**
 * <p>Removes control characters (char &lt;= 32) from both
 * ends of this String, handling {@code null} by returning
 * {@code null}.</p>
 *
 * <p>The String is trimmed using {@link String#trim()}.
 * Trim removes start and end characters &lt;= 32.
 * To strip whitespace use {@link #strip(String)}.</p>
 *
 * <p>To trim your choice of characters, use the
 * {@link #strip(String, String)} methods.</p>
 *
 * <pre>
 * StringUtils.trim(null)          = null
 * StringUtils.trim("")            = ""
 * StringUtils.trim("     ")       = ""
 * StringUtils.trim("abc")         = "abc"
 * StringUtils.trim("    abc    ") = "abc"
 * </pre>
 *
 * @param str  the String to be trimmed, may be null
 * @return the trimmed string, {@code null} if null String input
 */
public static String trim(final String str) {
    return str == null ? null : str.trim();
}

From my point of view there is no better way to implement it. Using Optionals is not an option. Therefore, the original solution idea in the question is confirmed.

CodePudding user response：

Typically this is done with the Apache Commons library's trim method. This library is so commonplace that it's basically part of Java. It will return null for null Strings. E.g. StringUtils.trim("myString "); would return "myString"

CodePudding user response：

String name = siteRequest.getName();

name == null ? name : 
name.trim();

String name = siteRequest.getName();

if(name != null)
  name.trim();

CodePudding user response：

Unfortunately Java still lacks a null-safe navigation operator. The closest way to replicate it would be with Optional:

String trimmed = Optional.ofNullable(untrimmed).map(String::trim).orElse(null);

However it's easy to see this does not beat a simple ternary most of the time. Where it does shine is if you have a long chain of potential nullables, and want to avoid nested ternaries:

String trimmed = Optional.ofNullable(request)
 .map(Request::getName)
 .map(String::trim)
 .orElse(null);

CodePudding user response：

As answered above simple use a util method to do this. Ideally, null conditional operator would have made it better, but that doesn't exist in java

But create a util method. flavor it as you need e.g from the above answers you can do

public static String trim(final String str) {
    return str == null ? null : str.trim();
}

or if you want to return a default values

public static String trim(final String str) {
    return str == null ? "default_value" : str.trim();
}

public static String trim(final String str, String defaultValue) {
    return str == null ? defaultValue : str.trim();
}

or if you want to use options

public static Option<String> trim(final String str) {
    return str == null ? Optional.nullable() : Optional.of(str.trim());
}

It purely depends on what you need and how your source code has been written.