转载

Guava 库

https://www.yiibai.com/guava

https://wizardforcel.gitbooks.io/guava-tutorial/content/1.html

com . google . common . base . Preconditions

checkArgument(i < j, "Expected i < j, but %s > %s", i, j);
checkNotNull(a, "parameter is Null");

com.google.common.base.Objects

equals,避免抛出NullPointerException

Objects.equal("a", "a"); // returns true
Objects.equal(null, "a"); // returns false
Objects.equal("a", null); // returns false
Objects.equal(null, null); // returns true

hashCode,

System.out.println(Objects.hashCode("a","b","c"));

Person person=new Person("peida",23);

System.out.println(Objects.hashCode(person));

com . google . common . cache . CacheBuilder

可设置过期的cache

https://segmentfault.com/a/1190000011105644

集合

http://ifeve.com/google-guava-collectionutilities/

com.google.common.collect.Maps

更简单的创建,newLinkedHashMap(),newConcurrentMap()

Map< String, String> aNewMap = Maps.newHashMap();

Lists,Sets

List<TypeThatsTooLongForItsOwnGood> list = Lists.newArrayList()

com.google.common.collect.Multimap

//Map<String, List<String>>

// lower -> a, b, c

// upper -> A, B

Multimap<String,String> multimap = ArrayListMultimap.create();

multimap.put("lower", "a");

multimap.put("lower", "b");

multimap.put("lower", "c");

multimap.put("upper", "A");

multimap.put("upper", "B");

Map<String, Collection<String>> map = multimap.asMap();

com.google.common.collect.Multiset

多个重复的值

Multiset<String> multiset = HashMultiset.create();

multiset.add("a");

multiset.add("a");

multiset.add("c");

Set<String> set = multiset.elementSet();

ImmutableMap,比java直接构建静态map要简单

Map<String, Integer> salary = ImmutableMap.<String, Integer> builder()

.put("John", 1000)

.put("Jane", 1500)

.put("Adam", 2000)

.put("Tom", 2000)

.build();

字符串

com.google.common.base.Joiner

Joiner joiner = Joiner.on("; ").skipNulls();
return joiner.join("Harry", null, "Ron", "Hermione");

com.google.common.base.Splitter

Splitter.on(',')
        .trimResults()
        .omitEmptyStrings()
        .split("foo,bar,,   qux");

Hash

com.google.common.hash.Hashing

md5

sha256

sha512

sha1

murmur3_128

murmur3_32

goodFastHash

原文  http://www.cnblogs.com/fxjwind/p/11727066.html
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