Commons Lang

Links

Maven

<dependency>
  <groupId>commons-lang</groupId>
  <artifactId>commons-lang</artifactId>
  <version>2.4</version>
</dependency>

Exception

getRootCause

To unwrap exception causes until you find the ultimate cause of the problem:

ExceptionUtils.getRootCause(Throwable throwable)

Hash Code

HashCodeBuilder

The HashCodeBuilder constructor has two parameters.

Two randomly chosen, non-zero, odd numbers must be passed in.
Ideally these should be different for each class, however this is not vital.
Prime numbers are preferred, especially for the multiplier (second parameter). Have a look at Prime number from Wikipedia for a list of prime numbers.

import org.apache.commons.lang.builder.HashCodeBuilder;

public class Person {

    /** The initial value for the hash code builder. */
    private static final int HASH_BUILDER_INITIAL = 17;
    /** The multiplier for the hash code builder. */
    private static final int HASH_BUILDER_MULTIPLIER = 37;

    String name;
    int age;
    boolean smoker;

    public int hashCode() {
        // you pick a hard-coded, randomly chosen, non-zero, odd number
        // ideally different for each class
        return new HashCodeBuilder(HASH_BUILDER_INITIAL, HASH_BUILDER_MULTIPLIER)
            .append(name)
            .append(age)
            .append(smoker)
            .toHashCode();
    }
}

String Escape Utilities

StringEscapeUtils

unescapeXml

unescapeXml

StringEscapeUtils.unescapeXml(line)

String Utilities

StringUtils.html

contains

contains:

import org.apache.commons.lang.StringUtils;
if (StringUtils.contains("image/jpeg", "jpeg")) {

deleteWhitespace

Add a sample for this method.

isBlank

Checks if a String is whitespace, empty (“”) or null:

if (StringUtils.isBlank(ext)) {

Note: Can also use isNotBlank…

isEmpty

Checks if a String is empty (“”) or null:

if (StringUtils.isEmpty(""))

Note: Can also use isNotEmpty…

Other

StringUtils.equalsIgnoreCase(null, "abc")             // false
StringUtils.substringAfterLast("foo.bar.baz", ".");   // "baz"
StringUtils.substringBeforeLast("foo.bar.baz", ".");  // "foo.bar"
StringUtils.split("foo.bar.baz", '.');                // { "foo", "bar", "baz" }
StringUtils.split("foo,  bar,baz", ", ");             // { "foo", "bar", "baz" }
StringUtils.leftPad("1", 3, '0');                     // "001"

remove

To return the body with the keyword removed:

final String value = StringUtils.remove(body, keyword);

replace

Replaces all occurrences of a String within another String:

String result = StringUtils.replace("aba", "a", "z")
// result == "zbz"

rightPad

import org.apache.commons.lang.StringUtils;

StringUtils.rightPad("Padme!", 10)

ToString

Implementing a simple toString() with Apache Commons

ToStringBuilder

public class Person {
    String name;
    int age;
    boolean smoker;

    public String toString() {
        return new ToStringBuilder(this).
            append("name", name).
            append("age", age).
            append("smoker", smoker).
            toString();
    }
}