Java Map 通过 key 或者 value 过滤的实例代码
今天写根过滤的时候一下子有点愣眼，先是想到用Java原生的map循环查出来，但是觉得太low，后面思考了一下可以用Java8的Lambda，写完了，又发现GoogleGuava有现成的方法，这里一一列出来，供参考使用。
首先提示，如果照搬我的代码的话别忘了引这些依赖
junit junit 4.12 test org.hamcrest hamcrest-core org.hamcrest hamcrest-library 1.3 test com.google.guava guava 25.1-jre
filterbykey
publicclassFilterMapByKeyTest{
privateMapWEEK=newHashMap<>();
@Before
publicvoidsetUp(){
WEEK.put(1,"Monday");
WEEK.put(2,"Tuesday");
WEEK.put(3,"Wednesday");
WEEK.put(4,"Thursday");
WEEK.put(5,"Friday");
WEEK.put(6,"Saturday");
WEEK.put(7,"Sunday");
}
/**
*Java8之前的版本
*/
@Test
publicvoidfilterMapByKey(){
Mapmap=newHashMap<>();
for(Map.Entryentry:WEEK.entrySet()){
if(entry.getKey()<=3){
map.put(entry.getKey(),entry.getValue());
}
}
assertThat(map.keySet(),contains(1,2,3));
}
/**
*Java8Lambda
*/
@Test
publicvoidfilterMapByKeyJava8Lambda(){
Mapmap=WEEK.entrySet().stream().filter(r->r.getKey()<=3)
.collect(Collectors.toMap(Map.Entry::getKey,Map.Entry::getValue));
assertThat(map.keySet(),contains(1,2,3));
}
/**
*GoogleGuava
*/
@Test
publicvoidfilterMapByKeyGuava(){
Mapmap=Maps.filterKeys(WEEK,r->r<=3);
assertThat(map.keySet(),contains(1,2,3));
}
}
filterbyvalue
publicclassFilterMapByValueTest{
privateMapWEEK=newHashMap<>();
@Before
publicvoidsetUp(){
WEEK.put(1,"Monday");
WEEK.put(2,"Tuesday");
WEEK.put(3,"Wednesday");
WEEK.put(4,"Thursday");
WEEK.put(5,"Friday");
WEEK.put(6,"Saturday");
WEEK.put(7,"Sunday");
}
/**
*Java8之前的版本
*/
@Test
publicvoidfilterMapByValue(){
Mapmap=newHashMap<>();
for(Map.Entryentry:WEEK.entrySet()){
if(entry.getValue().startsWith("S")){
map.put(entry.getKey(),entry.getValue());
}
}
assertThat(map.values(),contains("Saturday","Sunday"));
}
/**
*Java8Lambda
*/
@Test
publicvoidfilterMapByValueJava8Lambda(){
Mapmap=WEEK.entrySet().stream().filter(r->r.getValue().startsWith("S"))
.collect(Collectors.toMap(Map.Entry::getKey,Map.Entry::getValue));
assertThat(map.values(),contains("Saturday","Sunday"));
}
/**
*GoogleGuava
*/
@Test
publicvoidfilterMapByValueGuava(){
Mapmap=Maps.filterValues(WEEK,r->r.startsWith("S"));
assertThat(map.values(),contains("Saturday","Sunday"));
}
}
总结
以上所述是小编给大家介绍的JavaMap通过key或者value过滤的实例代码，希望对大家有所帮助，如果大家有任何疑问请给我留言，小编会及时回复大家的。在此也非常感谢大家对毛票票网站的支持！
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