Guava
Basic Utilities
Using/avoiding null
Optional
Preconditions
Ordering
Creation
Chaining
Application
Object methods
equals
hashCode
toString
compare/compareTo
Throwables
Collections
Immutable collections
New collection types
Multiset
Multimap
BiMap
Table
ClassToInstanceMap
RangeSet
Utility Classes
Iterables
Lists
Sets
Maps
Multisets
Multimaps
Tables
Extension Utilities
Forwarding Decorators
PeekingIterator
AbstractIterator
Caches
Applicability
Population
Eviction
Removal Listeners
Refresh
Timed Eviction
Size Caps
Garbage Collection
Explicit Removals
Features
Statistics
Interruption
Functional Idioms
Obtaining
Using Predicates
Using Functions
Concurrency
ListenableFuture
Service
Using
Implementations
Strings
Joiner
Splitter
CharMatcher
Charsets
Networking
InternetDomainName
Primitives
Primitive arrays
General utilities
Byte conversion
Unsigned support
Ranges
Building
Operations
Discrete Domains
I/O
Closing Resources
Hashing
BloomFilter
EventBus
Math
Integral
Overflow Checking
Floating Point
Reflection
TypeToken
Invokable
Dynamic Proxies
ClassPath
★CharMatcher
// \n\tを削除
str = CharMatcher.JAVA_ISO_CONTROL.removeFrom(sequence);
// 文字と数字を抽出
str = CharMatcher.JAVA_LETTER_OR_DIGIT.retainFrom(sequence);
// 改行→' '
str = CharMatcher.BREAKING_WHITESPACE.replaceFrom(sequence,' ');
str = CharMatcher.JAVA_UPPER_CASE.trimFrom(sequence);
str = CharMatcher.JAVA_UPPER_CASE.trimLeadingFrom(sequence);
str = CharMatcher.JAVA_UPPER_CASE.trimTrailingFrom(sequence);
// 大文字→?
str = CharMatcher.JAVA_UPPER_CASE.collapseFrom(sequence,'?');
// 小文字→?
str = CharMatcher.JAVA_LOWER_CASE.trimAndCollapseFrom(sequence,'?');
Charsets.UTF_8
Charsets.ISO_8859_1
Charsets.US_ASCII
Charsets.UTF_16
Charsets.UTF_16BE
Charsets.UTF_16LE
★IO
JDKと比較
BufferedReader reader
= new BufferedReader(new FileReader( new File("test.txt") ));
↓
BufferedReader reader = Files.newReader(new File("test.txt"), Charsets.UTF_8);
BufferedWriter writer = Files.newWriter(new File("test.txt"), Charsets.UTF_8);
} finally {
if (reader != null) {
try {
reader.close();
} catch (IOException e) {
logger.error("IOException occured", e);
}
}
}
↓
} finally {
//例外が発生してもスローしない
Closeables.closeQuietly(reader);
}
Writer writer = ...;
IOException thrown = null;
try {
writer.write(...);
} catch (IOException e) {
thrown = e;
} finally {
try {
writer.close();
} catch (IOException e) {
if (thrown == null) {
thrown = e;
} else {
logger.error("IOException occured", e);
}
}
}
if (thrown != null) {
throw thrown;
}
↓
Writer writer = ...;
boolean threw = true;
try {
writer.write(...);
threw = false;
} finally {
// threwがfalseの場合、発生した例外をスローする
// threwがtrueの場合、発生した例外をログ出力のみ行う
Closeables.close(writer, threw);
}
staticメソッド
Files.copy(new File("src.txt"), new File("dest.txt"));
Files.move(new File("src.txt"), new File("dest.txt"));
Files.createParentDirs(new File("aaa/bbb/ccc"));
//読み込み
String text = Files.toString(new File("test.txt"), Charsets.UTF_8);
byte[] bytes = Files.toByteArray(new File("test.txt"));
List<String> lines = Files.readLines(new File("test.txt"), Charsets.UTF_8);
//書き出し
Files.write("xxx".getBytes("UTF_8"), new File("test.txt"));
Files.write("xxx", new File("test.txt"), Charsets.UTF_8);
Files.append("xxx", new File("test.txt"), Charsets.UTF_8);
LineProcessor利用
String lines = Files.readLines(new File("test.txt"), Charsets.UTF_8,
new LineProcessor<String>() {
private List<String> lines = Lists.newArrayList();
@Override
public boolean processLine(String line) throws IOException {
if(line.startsWith("a")) {
lines.add(line);
}
return true;
}
@Override
public String getResult() {
return Joiner.on(",").join(lines);
}
}
);
★ListenableFutureについて
ListeningExecutorService executorService = MoreExecutors
.listeningDecorator(Executors.newCachedThreadPool());
final ListenableFuture<Integer> listenableFuture
= executorService.submit(new Callable<Integer>{...});
// 同期
Integer result = listenableFuture.get();
// 非同期：方式１
listenableFuture.addListener(new Runnable() {
@Override
public void run() {
Integer result = listenableFuture.get();
...
}
}, executorService);
// 非同期：方式２
Futures.addCallback(listenableFuture, new FutureCallback<Integer>() {
@Override
public void onSuccess(Integer result) {
...
}
@Override
public void onFailure(Throwable t) {
...
}
});
★Basic
Optional
nullを避けるための仕組み
Optional利用前
private static final Map<String, String> map
= new HashMap<String, String>();
static {
map.put("key1", "xxx");
map.put("key2", null);
}
String val = map.get("key2"); //null
String val = map.get("key3"); //null
Optional利用後
import com.google.common.base.Optional;
private static final Map<String, Optional<String>> map
= new HashMap<String, Optional<String>>();
static {
map.put("key1", Optional.of("xxx"));
map.put("key2", Optional.<String>absent());
}
Optional<String> val = map.get("key2"); //Nothing
System.out.printf("%s%n",
val == null ? "Unknown": val.isPresent() ? val: "Nothing");
Optional<String> val = map.get("key3"); //Unknown
System.out.printf("%s%n",
val == null ? "Unknown": val.isPresent() ? val: "Nothing");
Preconditions
防御的プログラミング
public void print(File file) {
checkState(!this.isClosed(), "message...");
checkNotNull(file, "message...");
checkArgument(file.isFile(), "message...");
checkArgument(file.canRead(), "message...");
checkArgument( list != null, "List must not be null" );
checkArgument( !list.isEmpty(), "List must not be empty" );
checkState( field.isPresent(), "Argument is not initialied" );
...
}
checkElementIndex(index, values.length, "message...");
Object methods
@override
public String toString(){
return Objects.toStringHelper(this).omitNullValues()
.add("x", this.x)
.toString(); // ClassName{x=1}
return Objects.toStringHelper("MyObject")
.add("x", 1)
.toString(); // MyObject{x=1}
}
@override
public int hashCode() {
return Objects.hashCode(title, author);
}
class Person implements Comparable<Person> {
...
public int compareTo(Person that) {
return ComparisonChain.start()
.compare(this.aString, that.aString)
.compare(this.anInt, that.anInt)
.compare(this.anEnum, that.anEnum,
Ordering.natural().nullsLast())
.result();
}
}
Encoding
import com.google.common.io.BaseEncoding;
String input = "...";
byte[] photo = BaseEncoding.base64().decode(input); // Base 64
byte[] photo = BaseEncoding.base64Url().decode(input); // web safe Base64
※Googleからプロフィール画像を取得する場合
https://www.googleapis.com/admin/directory/v1/users/xxx@example.com/photos/thumbnail
★Collections
Immutable collections
防御的コピー
public static final ImmutableSet<String> COLOR_NAMES = ImmutableSet.of(
"red", "blue", "purple");
class Foo {
private Set<Bar> bars;
public Foo(Set<Bar> bars) {
this.bars = ImmutableSet.copyOf(bars);
}
}
final List<String> list = ImmutableList.of("aa", "bb", "cc");
final Map<String, String> map
= ImmutableMap.of("key1", "value1", "key2", "value2");
Map<Integer, String> numbers =
ImmutableMap.<Integer, String>builder()
.put(1, "one")
.put(2, "two")
.build();
New collection types
MultiSet 同じ値を持つことができるSet
MultiMap キーに対する値を複数もつことができるMap（値の管理：ListMultiMapとSetMultiMap）
BiMap キーだけでなく値もユニークさを保証するMap
Table 行と列の構造を持ったコレクション（２次元配列と違い）
ClassToInstanceMap クラスの型をキーにするMap
RangeSet / RangeMap 範囲のコレクション
JDKと比較
if (!map.contains(k)) {
map.put(k, new ArrayList());
}
map.get(k).add(v);
↓
// MultiMap
map.put(k, v);
List<B> blist = new ArrayList<B>(alist.size());
for (A a : alist) {
blist.add(new B(a));
}
↓
List<B> blist = Lists.transform(alist,
new Function<A, B>(){
@Override
public B apply(A a) {
return new B(a);
}
}
);
Map<KeyA, Map<KeyB, Value>> nestedMap = ...
Map<KeyB, Value> innerMap = nestedMap.get(keyA);
Value value;
if (innerMap == null) {
value = null;
} else {
value = innerMap.get(keyB);
}
↓
Table<KeyA, KeyB, Value> table = ...
Value value = table.get(keyA, keyB);
Utility Classes (import com.google.common.collect)
List<Product> products = ...
List<Integer> ids = Lists.transform(products,
new Function<Product, Integer>(){
public Integer apply(Product p) {
return p.getId();
}
});
Map<String, String> map = Maps.newLinkedHashMap();
Map<String, String> map = Maps.newHashMap();
List<Product> products = ...
Map<Integer, Product> productById = Maps.uniqueIndex(products,
new Function<Product, Integer>(){
public Integer apply(Product p) {
return p.getId();
}
});
Iterable<Integer> concatenated = Iterables.concat(
Ints.asList(1, 2, 3),
Ints.asList(4, 5, 6)
);
Multiset<String> multiSet = HashMultiset.create();
multiSet.add("key");
String theElement = Iterables.getOnlyElement(multiSet);
Iterable<String> i = ...;
String[] array = Iterables.toArray(i, String.class);
List<Product> products = ...
Product p = Iterables.find(products,
new Predicate<Product>(){
public boolean apply(Product p) {
return p.getId() == 101;
}
});
Iterable<Product> filtered = Iterables.filter(products,
new Predicate<Product>(){
public boolean apply(Product p) {
return "sport".equals(p.getCategory());
}
});