Sunday, January 4, 2015

Google Gauva API in a one glance: Joiner



@GwtCompatible
public class Joiner
extends Object
An object which joins pieces of text (specified as an array, Iterable, varargs or even a Map) with a separator. It either appends the results to an Appendable or returns them as a String.

In the following example, we join a List of String into one String using the “#” as a separator:
/**
*
*/
package com.rajkrrsingh.test.guava;

import java.util.Arrays;
import java.util.Collection;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;

import com.google.common.base.CharMatcher;
import com.google.common.base.Function;
import com.google.common.base.Functions;
import com.google.common.base.Joiner;
import com.google.common.base.Predicate;
import com.google.common.base.Predicates;
import com.google.common.collect.Collections2;
import com.google.common.collect.Iterables;

/**
* @author rks
* @04-Jan-2015
*/
public class GuavaJoinerDemo {

public static void main(String[] args) {
joinerDemo();
}


// tranform a collection into a sting
public static void joinerDemo(){
List<String> list = Arrays.asList("RKS","John","Nick","Harry");
System.out.println(Joiner.on("#").join(list));

List<String> list1 = Arrays.asList("RKS","John",null,"Nick","Harry");
//skip nulls
System.out.println(Joiner.on("#").skipNulls().join(list1));
//defualt value for null
System.out.println(Joiner.on("#").useForNull("BLANK").join(list1));

// joiner on Map
Map<String, String> map = new HashMap<String, String>();
map.put("key1", "value1");
map.put("key2", "value2");
map.put("key3", "value3");
map.put("key4", "value4");

System.out.println(Joiner.on("#").withKeyValueSeparator(":").join(map));
}
}
Please follow my comments in the code to relate with the output
RKS#John#Nick#Harry
RKS#John#Nick#Harry
RKS#John#BLANK#Nick#Harry
key4:value4#key3:value3#key2:value2#key1:value1

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