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把list中的null值用各类方法删除

1kesou 2022-12-02 阅读 50


比如要把一个LIST中的所有NULL值都取消,则可以:

1) JAVA 7及以下版本:

@Test
public removeAllNullsFromListWithJava7OrLower() {

List<String> list =
new ArrayList<>(Arrays.asList("A", null, "B", null));

list.removeAll(Collections.singleton(null));

assertThat(list, hasSize(2));
}

2) 如果是JAVA 8以上,可以更优雅
    

@Test
public removeAllNullsFromListWithJava8() {

List<String> list =
new ArrayList<>(Arrays.asList("A", null, "B", null));

list.removeIf(Objects::isNull);

assertThat(list, hasSize(2));
}

如果想用一个新得LIST去装载,则可以:
    

@Test
public removeAllNullsFromListWithJava8() {

List<String> list =
new ArrayList<>(Arrays.asList("A", null, "B", null));

List<String> newList = list.stream().filter(Objects::nonNull)
.collect(Collectors.toList());

assertThat(list, hasSize(4));
assertThat(newList, hasSize(2));
}

3) 也可以用著名得apache common工具库去做:
 

@Test
public removeAllNullsFromListWithApacheCommons() {

List<String> list =
new ArrayList<>(Arrays.asList("A", null, "B", null));

CollectionUtils.filter(list, PredicateUtils.notNullPredicate());

assertThat(list, hasSize(2));
}

4) GOOGLE GUVA库:
  

@Test
public removeAllNullsFromListUsingGuava() {

List<String> list =
new ArrayList<>(Arrays.asList("A", null, "B", null));

List<String> newList = new ArrayList<>(
Iterables.filter(list, Predicates.notNull()));

assertThat(list, hasSize(4));
assertThat(newList, hasSize(2));
}

 

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