Google Guava学习计划第一章Guava Utilities—Function_Predicate_Maps_Sets

主要分为三个部分：

第一步部分Function部分

* 1.Function 接口 输入一个对象，返回一个对象
* 2.Functions作用:是一个工具类，和集合+Function集合起来
* 3.List<Obj> ->List<String> or Map<String,Obj>
* 4.Sets 集合的交并差
* 5.Maps 工具类是对Map的操作 很多特殊种类的map

package matrixOnto.deal.Util.GuavaFunctional;

import com.google.common.base.*;
import com.google.common.collect.*;

import javax.annotation.Nullable;
import java.util.*;

import static org.hamcrest.CoreMatchers.equalTo;
import static org.hamcrest.MatcherAssert.assertThat;

public class FunctionsDemo{

public static void main(String[] args) {
//1.List<Obj> ->List<String>
ArrayList<User> users = Lists.newArrayList(new User("Jone", 27, 15000d), new User("Vieech", 30, 10000d), new User("Hopy", 4, 50l));
List<String> strings = commonTransFunction(users);
System.out.println("x");
//2.关于Functions的用法 将List转换为Map
ImmutableMap<String, User> functionsMap = commonTransFunctionToMap(users);
Function<String, User> lookUp = Functions.forMap(functionsMap);
//提供给后面compose的方法
Predicate<String> compose = Predic
4000
ates.compose(new Predicate<User>() {
@Override
public boolean apply(@Nullable User user) {
Preconditions.checkNotNull(user);
if (user.getUserName().equalsIgnoreCase("Jone")) {
return true;
}
return false;
}

@Override
public boolean equals(@Nullable Object o) {
return false;
}
}, lookUp);
//流程是  Jone#27#15000.0 查询lookUp等到 User,通过Predicate<User>进行断言，看是否满足
//common 流程是 输入得到Function的输出，传入Predicate进行断言，返回结果
boolean jone1 = compose.apply("Jone#27#15000.0");
assertThat(jone1,equalTo(true));
//3.List<Obj> ->Map<String,Obj>
ImmutableMap<String, User> map = commonTransFunctionToMap(users);
System.out.println("xx");
//4.Sets 集合的交并差
HashSet<String> var1 = Sets.newHashSet("2", "5", "55");
HashSet<String> var2 = Sets.newHashSet("2", "6", "5");
HashSet<String> var3 = Sets.newHashSet("20", "9", "955");
//4.1集合之间的不同
Sets.SetView<String> difference1 = Sets.difference(var1, var2);
Sets.SetView<String> difference2 = Sets.difference(var2, var1);
for (String str:difference1){
System.out.println(str);
}
//4.2集合之间的对称差
Sets.SetView<String> symmetricDifference = Sets.symmetricDifference(var1, var2);
//4.3 集合之间的交集
Sets.SetView<String> intersection = Sets.intersection(var1, var3);
//4.4 集合之间的并集
Sets.SetView<String> union = Sets.union(var1, var2);
System.out.println("xx");
//5.Maps 工具类是对Map的操作
//5.1 采用ArrayList一键多值 相同的值可以重复
ArrayListMultimap<String, String> arrayListMultimap = ArrayListMultimap.create();
arrayListMultimap.put("foo","1");
arrayListMultimap.put("foo","2");
arrayListMultimap.put("foo","3");
arrayListMultimap.put("bar","a");
arrayListMultimap.put("bar","a");
arrayListMultimap.put("bar","b");
for (String key:arrayListMultimap.keySet()){
System.out.println("key="+key+",value="+arrayListMultimap.get(key));
}
//key=bar,value=[a, a, b] //这里可以存在重复的key指
//key=foo,value=[1, 2, 3]

//5.2 采用HashTable保存一键多值 相同的值不能重复
HashMultimap<String, String> hashMultimap = HashMultimap.create();
hashMultimap.put("foo","1");
hashMultimap.put("foo","2");
hashMultimap.put("foo","3");
hashMultimap.put("bar","a");
hashMultimap.put("bar","a");
hashMultimap.put("bar","b");
System.out.println(hashMultimap);
//{bar=[a, b], foo=[1, 2, 3]}   其中重复的bar-a bar-a 只保留了一个

//5.3 多键类Table 理解为Key key2 value的Map
HashBasedTable<Object, Object, Object> kkvMap = HashBasedTable.create();
kkvMap.put(1,1,"book");kkvMap.put(1,2,"turkey");kkvMap.put(2,10,"apple");kkvMap.put(2,2,"orange");
assertThat(kkvMap.get(1,2),equalTo("turkey"));
assertThat(kkvMap.contains(2,3),equalTo(false));
assertThat(kkvMap.containsRow(2),equalTo(true));
boolean book = kkvMap.containsValue("book");
boolean columnOk = kkvMap.containsColumn(10);
Map<Object, Object> row = kkvMap.row(1);//得到Map
Map<Object, Object> column = kkvMap.column(2);//得到comkey为2的Map<key=rowKey,value=value>
Set<Object> columnKeySet = kkvMap.columnKeySet();
Set<Object> rowKeySet = kkvMap.rowKeySet();
//5.4 可以通过value获取Key的HashBiMap
HashBiMap biMap=HashBiMap.create();
biMap.put("hello","world");
//biMap.put("abc","world");//会失败
biMap.forcePut("abc","world");//强制put
biMap.put("123","tell");
biMap.put("123","none");//none会覆盖上面的tell
//*****键值互换得到新的map
BiMap inverse = biMap.inverse();
assertThat(inverse.get("none"),equalTo("123"));
System.out.println("xx");
//5.5 不可变集合类 ImmutableListMultMap
//不可变的集合类，都有一个Builder的内部类，不可以修改添加
ImmutableListMultimap<Integer, String> immutableListMap = new ImmutableListMultimap.Builder<Integer, String>()
.put(1, "hello")
.putAll(2, "abc", "log", "in")
.putAll(3, "get", "up").build();
//immutableListMap.put(1,"3"); 报错，不支持重新Put
System.out.println(immutableListMap.get(2));
//6 关于Range的定义，开区间和闭区间
Range<String> closed = Ranges.closed("a", "z");
boolean b = closed.contains("b");
Range<Integer> open = Ranges.open(1, 7);
boolean contains = open.contains(2);
Predicate<User> composeInd = Predicates.compose(open, new Function<User, Integer>() {
@Nullable
@Override
public Integer apply(@Nullable User user) {
Preconditions.checkNotNull(user);
return user.getAge();
}
});
boolean jone = composeInd.apply(new User("Jone", 2, 15000d));
System.out.println(closed);

}

/**
* 将List<Obj> <--> 转换成 List<String>
* @return
*/
private List<String> transFunctionOne() {
ArrayList<User> users = Lists.newArrayList(new User("Jone", 27, 15000d), new User("Vieech", 30, 10000d), new User("Hopy", 4, 50l));
Function<User,String> function = new Function<User, String>() {
@Nullable
@Override
public String apply(@Nullable User user) {
Preconditions.checkNotNull(user);
return Joiner.on("#").join(user.getUserName(),user.getAge(),user.getSalary());
}
@Override
public boolean equals(@Nullable Object o) {
return false;
}
};
FluentIterable<String> transform = FluentIterable.from(users).transform(function);
ArrayList<String> strings = Lists.newArrayList(transform);
return strings;
}

/**
* 比较抽象的一个通用的解析方法
* CommonVo 所有的不同的类型的类型都继承
* 抽取出返回的通用的List
* 适用的场景是:通用的将List<VO> 转换成List<String>
* @param inputs
* @param <I>
* @return
*/
private static <I> List<String> commonTransFunction(List<I> inputs ) {
Function<I,String> function = new Function<I, String>() {
@Nullable
@Override
public String apply(@Nullable I input) {
Preconditions.checkNotNull(input);
//在这里也可以采用switch的方式，通过判断不同的类型的input来进行特殊的返回值的包装
if (input instanceof CommonVo){
CommonVo var1 = (CommonVo) input;
return Joiner.on("#").join(var1.getUserName(),var1.getAge(),var1.getSalary());
}
return "";
}
@Override
public boolean equals(@Nullable Object o) {
return false;
}
};
FluentIterable<String> transform = FluentIterable.from(inputs).transform(function);
ArrayList<String> strings = Lists.newArrayList(transform);
return strings;
}

/**
* 比较抽象的一个通用的解析方法
* CommonVo 所有的不同的类型的类型都继承
* 抽取出返回的通用的Map
* 适用的场景是:通用的将List<VO> 转换成Map<String,Vo>
* @param inputs
* @param <I>
* @return
*/
private static <I> ImmutableMap<String,I> commonTransFunctionToMap(List<I> inputs ) {
Function<I,String> function = new Function<I, String>() {
@Nullable
@Override
public String apply(@Nullable I input) {
Preconditions.checkNotNull(input);
//在这里也可以采用switch的方式，通过判断不同的类型的input来进行特殊的返回值的包装
if (input instanceof CommonVo){
CommonVo var1 = (CommonVo) input;
return Joiner.on("#").join(var1.getUserName(),var1.getAge(),var1.getSalary());
}
return "";
}
@Override
public boolean equals(@Nullable Object o) {
return false;
}
};
ImmutableMap<String, I> stringIImmutableMap = Maps.uniqueIndex(inputs, function);
return stringIImmutableMap;
}

static abstract class CommonVo{
protected String userName;
protected int age;
protected double salary;

public CommonVo(String userName, int age, double salary) {
this.userName = userName;
this.age = age;
this.salary = salary;
}

public String getUserName() {
return userName;
}

public CommonVo setUserName(String userName) {
this.userName = userName;
return this;
}

public int getAge() {
return age;
}

public CommonVo setAge(int age) {
this.age = age;
return this;
}

public double getSalary() {
return salary;
}

public CommonVo setSalary(double salary) {
this.salary = salary;
return this;
}

}

static class User extends CommonVo {

public User(String userName, int age, double salary) {
super(userName, age, salary);
}
}
}

package matrixOnto.deal.Util.GuavaFunctional;import com.google.common.base.*;import com.google.common.collect.ImmutableMap;import com.google.common.collect.Iterables;import com.google.common.collect.Lists;import com.google.common.collect.Maps;import javax.annotation.Nullable;import java.util.ArrayList;import java.util.List;import static org.hamcrest.CoreMatchers.equalTo;import static org.junit.Assert.assertThat;/*** Created by mengxiaopeng on 2017/12/12.* matrixOnto.deal.Util.GuavaFunctional* 1.Predicate接口  输入一个T 返回一个Boolean 一般用于集合过滤等* 2.Predicates的用法 结合集合开始过滤。* 3.将List<Persion> <=Maps.uniqueIndex=>转换成Map<String,Persion>*/public class PredicatesDemo {public static void main(String[] args) {PredicatesDemo demo = new PredicatesDemo();//1.采用正则表达式Predicate<Object> objectPredicate = Predicates.alwaysFalse();Predicate<CharSequence> charSequencePredicate = Predicates.containsPattern("\\*");boolean apply = charSequencePredicate.apply("12*3");assertThat(apply, equalTo(true));//2.关于Predicates 中具体的方法配合集合进行过滤ArrayList<User> users = Lists.newArrayList(new User("Jone", 27, 15000d), new User("Vieech", 30, 10000d), new User("Hopy", 4, 50l));List<User> ss = demo.listFilter(users, "Jone", 3, "ors");System.out.println(ss);//3.compaose 用法//3.1.将List转换为MapFunction function = demo.getNameFunction();ImmutableMap<String, User> immutableMap = Maps.uniqueIndex(users, function);//3.2.将Map转换成FunctionFunction<String, User> lookUp = Functions.forMap(immutableMap);//3.3 采用Predicates的compose方法Predicate<String> compose = Predicates.compose(demo.filterAge(10), lookUp);boolean xx = compose.apply("Jone");}/*** 根据输入的inputs 对name age 做过滤，过滤的模式取决于type(and or模式)** @param inputs* @param name* @param age* @param type* @return*/public List<User> listFilter(List<User> inputs, String name, int age, String type) {Preconditions.checkNotNull(inputs, "input soures can not be null..");Predicate<User> predicateName = filteName(name);Predicate<User> predicateAge = filterAge(age);//将两个Predicate进行并集 合并两个过滤的结果Predicate or = Predicates.or(predicateAge, predicateName);//将两个Predicate进行交集，先成交集的Predicate然后进行过滤Predicate<User> and = Predicates.and(predicateAge, predicateName);if ("or".equalsIgnoreCase(type)) {and = or;}Iterable<User> filter = Iterables.filter(inputs, and);ArrayList arrayList = Lists.newArrayList(filter);return arrayList;}/*** 其中输入时User对象，返回时String对象** @return*/private Function getNameFunction() {return new Function<User, String>() {@Nullable@Overridepublic String apply(@Nullable User user) {Preconditions.checkNotNull(user);return user.getUserName();}@Overridepublic boolean equals(@Nullable Object o) {return false;}};}/*** 过滤name** @param name*/private Predicate<User> filteName(final String name) {return new Predicate<User>() {@Overridepublic boolean apply(@Nullable User user) {Preconditions.checkNotNull(user);if (user.getUserName().equalsIgnoreCase(name)) {return true;}return false;}@Overridepublic boolean equals(@Nullable Object o) {return false;}};}/*** 根据age过滤** @param filterAge*/private Predicate<User> filterAge(int filterAge) {return new Predicate<User>() {@Overridepublic boolean apply(@Nullable User user) {Preconditions.checkNotNull(user);if (user.getAge() > filterAge) {return true;}return false;}@Overridepublic boolean equals(@Nullable Object o) {return false;}};}static class User {private String userName;private int age;private double salary;public User(String userName, int age, double salary) {this.userName = userName;this.age = age;this.salary = salary;}public String getUserName() {return userName;}public User setUserName(String userName) {this.userName = userName;return this;}public int getAge() {return age;}public User setAge(int age) {this.age = age;return this;}public double getSalary() {return salary;}public User setSalary(double salary) {this.salary = salary;return this;}}}

第三部分 采用枚举实现单列

SingleTonDemo

package matrixOnto.deal.Util.GuavaFunctional;/*** Created by mengxiaopeng on 2017/12/12.* matrixOnto.deal.Util.GuavaFunctional* 枚举直接实现单列模式 简洁 而且*/public enum SingleTonDemo {INSTANCE;SingleTonDemo() {System.out.println("SingTon Con...Times");}public void om(){System.out.println("Om ways..");}public static void main(String[] args) {SingleTonDemo.INSTANCE.om();SingleTonDemo.INSTANCE.om();SingleTonDemo.INSTANCE.om();}}

喜剧之王