Commit 9488578

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putIfAbsent + doc update

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Lines changed: 10 additions & 1 deletion

Original file line number	Diff line number	Diff line change
@@ -52,6 +52,9 @@ In `Map.Entry`:
`52`	`52`	* `default V putIfAbsent(K key, V value)`- If the specified key is
`53`	`53`	`not already associated with a value (or is mapped to null) associates`
`54`	`54`	`it with the given value and returns null, else returns the current value.`
	`55`	`+`
	`56`	+ _Remark_: `map.putIfAbsent(1, null);` is OK
	`57`	`+`
`55`	`58`	* `default boolean remove(Object key, Object value)`
`56`	`59`	* `default void replaceAll(BiFunction<? super K, ? super V, ? extends V> function)`
`57`	`60`	* `default boolean replace(K key, V oldValue, V newValue)`
`@@ -90,4 +93,10 @@ We provide tests for above mentioned methods.`
`90`	`93`	```
`91`	`94`	`map.getOrDefault(1, "NOT-FOUND");`
`92`	`95`	```
`93`		`-1. modifying`
	`96`	`+1. modifying`
	`97`	`+ * putIfAbsent - good way of initializing entries in map`
	`98`	+ ```
	`99`	`+ Map<String, Integer> counter = new HashMap<>();`
	`100`	`+`
	`101`	`+ counter.putIfAbsent("11-u", 0);`
	`102`	+ ```

Lines changed: 44 additions & 0 deletions

Original file line number	Diff line number	Diff line change
`@@ -0,0 +1,44 @@`
	`1`	`+import org.junit.Test;`
	`2`	`+`
	`3`	`+import java.util.HashMap;`
	`4`	`+import java.util.Map;`
	`5`	`+`
	`6`	`+import static org.hamcrest.CoreMatchers.is;`
	`7`	`+import static org.hamcrest.MatcherAssert.assertThat;`
	`8`	`+`
	`9`	`+/**`
	`10`	`+ * Created by mtumilowicz on 2018年11月09日.`
	`11`	`+ */`
	`12`	`+public class MapModifyingTest {`
	`13`	`+`
	`14`	`+ @Test`
	`15`	`+ public void putIfAbsent_exists() {`
	`16`	`+ Map<Integer, String> map = new HashMap<>();`
	`17`	`+`
	`18`	`+ map.put(1, "1");`
	`19`	`+`
	`20`	`+ map.putIfAbsent(1, "2");`
	`21`	`+`
	`22`	`+ assertThat(map.get(1), is("1"));`
	`23`	`+ }`
	`24`	`+`
	`25`	`+ @Test`
	`26`	`+ public void putIfAbsent_notExists() {`
	`27`	`+ Map<Integer, String> map = new HashMap<>();`
	`28`	`+`
	`29`	`+ map.putIfAbsent(1, "1");`
	`30`	`+`
	`31`	`+ assertThat(map.get(1), is("1"));`
	`32`	`+ }`
	`33`	`+`
	`34`	`+ @Test`
	`35`	`+ public void putIfAbsent_mappedToNull() {`
	`36`	`+ Map<Integer, String> map = new HashMap<>();`
	`37`	`+`
	`38`	`+ map.put(1, null);`
	`39`	`+`
	`40`	`+ map.putIfAbsent(1, "1");`
	`41`	`+`
	`42`	`+ assertThat(map.get(1), is("1"));`
	`43`	`+ }`
	`44`	`+}`

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