Skip to main content

Guava: String Manipulation with CharMatcher, Spliter and Joiner

Guava has very simple and powerful string manipulation mechanism. Here are some classes like CharMatcher, Splitter and Joiner provides very simple way to perform some complex operation on string collections.

CharMatcher
Determines a true or false value for any Java char value, just as Predicate does for any Object.[from guava doc]


Use a predefined constant (predefine CharMatcher)
  • CharMatcher.WHITESPACE (Java whitespace character)
  • CharMatcher.JAVA_DIGIT
  • CharMatcher.JAVA_LETTER
  • CharMatcher.JAVA_LOWER_CASE 
  • CharMatcher.JAVA_UPPER_CASE 
  • CharMatcher.ASCII
  • CharMatcher.ANY
  • ...

String str = "FirstName LastName +1 123 456 789 !@#$%^&*()_+|}{:\"?><";

CharMatcher.DIGIT.retainFrom(str);

Output:->
"1123456789"


CharMatcher.JAVA_LETTER.retainFrom(str);

Output:->
"FirstNameLastName"


CharMatcher.JAVA_LETTER_OR_DIGIT.retainFrom(str);

Output:->
"FirstNameLastName1123456789"


CharMatcher.ANY.countIn(str)

Output:->
54


CharMatcher.DIGIT.countIn(str);

Output:->
10



Use a factory method
  • CharMatcher.is('x')
  • CharMatcher.isNot('_')
  • CharMatcher.oneOf("aeiou").negate()
  • CharMatcher.inRange('a', 'z').or(inRange('A', 'Z'))
  • ...

Use Combination
  • CharMatcher and(CharMatcher other) 
  • CharMatcher or(CharMatcher other) 
  • CharMatcher negate() 


String str = "FirstName LastName +1 123 456 789 !@#$%^&*()_+|}{:\"?><";

CharMatcher.JAVA_LOWER_CASE.negate().retainFrom(str);

Output:->
"FN LN +1 123 456 789 !@#$%^&*()_+|}{:\"?><"


CharMatcher.JAVA_DIGIT.or(CharMatcher.anyOf("aeiou")).retainFrom(str);

Output:->
"iaeaae1123456789"




Splitter
An object that divides strings (or other instances of CharSequence) into substrings, by recognizing a separator (a.k.a. "delimiter") which can be expressed as a single character, literal string, regular expression, CharMatcher, or by using a fixed substring length. [from guava doc]

String str = "test1, , test2, test3";
Iterable<String> strArr = Splitter.on(',')
  .trimResults()
  .omitEmptyStrings()
  .split(str);

Output:->
["test1", "test2", "test3"]


String str = "key1: 1; key2: 2  ; key3: 3";
Map<String, String> m = Splitter.on(';')
  .trimResults()
  .withKeyValueSeparator(":")
  .split(str);

Output:->
{key1= 1, key2= 2, key3= 3}


private static final Splitter COMMA_SPLITTER = Splitter.on(',')
       .trimResults()
       .omitEmptyStrings();
COMMA_SPLITTER.split("foo, ,bar, quux,");

Output:->
["foo", "bar", "quux"]




Joiner
An object which joins pieces of text (specified as an array, Iterable, varargs or even a Map) with a separator.
If neither skipNulls() nor useForNull(String) is specified, the joining methods will throw NullPointerException if any given element is null.[from guava doc]

ArrayList<String> strArr1 = Lists.newArrayList(
                         "test1","test2","test3",null,"test4",null,null);

Joiner.on(';')
  .skipNulls()
  .join(strArr1);

Output:->
"test1;test2;test3;test4"


Joiner.on(';')
  .useForNull("_")
  .join(strArr1);

Output:->
"test1;test2;test3;_;test4;_;_"


Joiner can be use for Map
Map<String, String> map = Maps.newHashMap();
map.put("key1", "value1");
map.put("key2", "value2");
map.put("key3", null);
map.put("key4", "value3");
 
Joiner.on(';')
 .useForNull("NULL")
 .withKeyValueSeparator("=")
 .join(map);

Output:->
"key4=value3;key3=NULL;key2=value2;key1=value1"

Advance use-case for joiner
Skip null and trim the result before joining


ArrayList<String> strArr = Lists.newArrayList(
                         " test1","test2 "," test3 ",null,"test4",null,null,"", "  ");
Predicate<String> EMPTY_OR_NULL_FILTER = new Predicate<String>() {
 @Override
 public boolean apply(String str){
  str = Strings.nullToEmpty(str).trim();
  return !Strings.isNullOrEmpty(str);
 }
};

Function<String, String> TRIM_RESULT = new Function<String, String>(){
 @Override
 public String apply(String str){
  return Strings.nullToEmpty(str).trim();
 }
};
  
String joinStr = Joiner.on(';')
 .skipNulls()
 .join(Collections2.transform(Collections2.filter(strArr, EMPTY_OR_NULL_FILTER), TRIM_RESULT));

Output:->
"test1;test2;test3;test4"


Comments

Popular posts from this blog

ERROR: Ignored call to 'alert()'. The document is sandboxed, and the 'allow-modals' keyword is not set.

Recently I found this issue while writing code snippet in "JSFiddle". And after searching, found this was happening because of new feature added in "Chrome 46+". But at the same time Chrome doesn't have support for "allow-modals" property in "sandbox" attribute.

Chromium issue for above behavior:
https://codereview.chromium.org/1126253007

To make it work you have to add "allow-scripts allow-modals" in "sandbox" attribute, and use "window.alert" instead of "alert".



<!-- Sandbox frame will execute javascript and show modal dialogs --> <iframe sandbox="allow-scripts allow-modals" src="iframe.html"> </iframe>


Feature added: Block modal dialog inside a sandboxed iframe.
Link: https://www.chromestatus.com/feature/4747009953103872

Feature working Demo page:
https://googlechrome.github.io/samples/block-modal-dialogs-sandboxed-iframe/index.html



JavaScript [ExtJs3]: EditorGridPanel Read-Only (dynamically)

Many time we face the scenerio where we have to make the editor grid read-only dynamically.


Ext.override(Ext.ux.grid.CheckColumn, { editable: true, onMouseDown: function (e, t) { if (Ext.fly(t).hasClass(this.createId())) { e.stopEvent(); var me = this, grid = me.grid, view = grid.getView(), index = view.findRowIndex(t), colindex = view.findCellIndex(t), record = grid.store.getAt(index); if (!grid.isReadOnly && grid.colModel.isCellEditable(colindex, index)) { record.set(me.dataIndex, !record.data[me.dataIndex]); } } } }); var grid = new Ext.grid.EditorGridPanel({ ... isReadOnly: true, //set to flag to make check column readonly ... }); //to make other column readonly grid.on('beforeedit', function () { return false; });

JavaScript [ExtJs3]: Total “Record” count in filtered store

There is two way to get record count from the Store
store.getTotalCount() This function depend on server response value. For accuracy of the value, property shell if return by the server.

Property name for the diff. reader:
totalProperty for JsonReader, totalRecords for XmlReaderstore.getCount() Will return you the number of record from the store.
Or if you have filter on the store, it will give you the number of filtered record.
But if you want to get the total number of record regardless filtering, Then it will be like this

var totalRecords = store.snapshot ? store.snapshot.length : store.getCount();
“snapshot” is the variable in “Store” which hold the actual data in case if you have applied a filter.