Google Guava集合库
Google Collections
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Guava:google的工程师利用传说中的"20%时间"开发的集合库,它是对jdk提供的扩展,提供了很多实用的类来简化代码
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github地址:https://github.com/google/guava
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可以使用HugeChm把文档打包成chm格式
Demo
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import com.google.common.collect.ImmutableList;
public class Demo01 {
public static void main(String[] args) {
List<String> list = new ArrayList<String>();
list.add("a");
list.add("b");
list.add("c");
//对原有的list进行包装,相当于原有List的一个视图,快照,不够安全
List<String> readList = Collections.unmodifiableList(list);
//readList.add("d");
list.add("d");//改变原有List 视图也一起改变
//对比Guava 对只读设置安全可靠 并且相对简单
List<String> immutableList = ImmutableList.of("a","b","c");
immutableList.add("d");
}
}import java.text.SimpleDateFormat;
import java.util.Collection;
import java.util.List;
import java.util.Set;
import com.google.common.base.Function;
import com.google.common.base.Functions;
import com.google.common.base.Predicate;
import com.google.common.collect.Collections2;
import com.google.common.collect.Lists;
import com.google.common.collect.Sets;
/**
* 函数式编程 解耦
* 1.Predicate 断言
* 2.Function 函数
* @author Matrix42
*
*/
public class Demo02 {
public static void main(String[] args) {
test1();
test2();
test3();
}
//过滤器
public static void test1(){
//创建List 静态初始化
List<String> list = Lists.newArrayList("moom","som","dad");
//找出回文
Collection<String> palindromeList = Collections2.filter(list, new Predicate<String>() {
@Override
public boolean apply(String input) {
//业务逻辑
return new StringBuilder(input).reverse().toString().equals(input);
}
});
for (String string : palindromeList) {
System.out.println(string);
}
}
//类型转换
public static void test2(){
Set<Long> timeSet = Sets.newHashSet();
timeSet.add(10000000L);
timeSet.add(999999999999999999L);
timeSet.add(20000000000L);
Collection<String> timeStrCol = Collections2.transform(timeSet, new Function<Long, String>() {
@Override
public String apply(Long input) {
return new SimpleDateFormat("yyyy-MM-dd").format(input);
}
});
for (String string : timeStrCol) {
System.out.println(string);
}
}
//组合式函数编程
//确保容器中的字符串长度不超过5,超过进行截取,转换为大写
public static void test3(){
List<String> list = Lists.newArrayList("lorinda","haha","happiness");
Function<String, String> f1 = new Function<String,String>() {
@Override
public String apply(String input) {
return input.length()>5?input.substring(0,5):input;
}
};
Function<String, String> f2 = new Function<String,String>() {
@Override
public String apply(String input) {
return input.toUpperCase();
}
};
//对函数进行组合
Function<String, String> f = Functions.compose(f1, f2);
Collection<String> resultCol = Collections2.transform(list, f);
for (String string : resultCol) {
System.out.println(string);
}
}
}import java.util.Set;
import com.google.common.base.Preconditions;
import com.google.common.collect.Constraint;
import com.google.common.collect.Constraints;
import com.google.common.collect.Sets;
/**
* 加入约束条件:非空,长度验证
* Constraint
* @author Matrix42
*
*/
public class Demo03 {
public static void main(String[] args) {
Set<String> sets = Sets.newHashSet();
//创建约束
Constraint<String> constraint = new Constraint<String>(){
@Override
public String checkElement(String element) {
//非空验证
Preconditions.checkNotNull(element);
//长度验证
Preconditions.checkArgument(element.length()>=5&&element.length()<=20);
return element;
}
};
Set<String> cs = Constraints.constrainedSet(sets, constraint);
//cs.add(null);
//cs.add("good");
cs.add("lorinda");
for (String string : cs) {
System.out.println(string);
}
}
}import java.util.Set;
import com.google.common.collect.Sets;
import com.google.common.collect.Sets.SetView;
/**
* 集合的操作:交集 差集 并集
* @author Matrix42
*
*/
public class Demo04 {
public static void main(String[] args) {
Set<Integer> sets =Sets.newHashSet(1,2,3,4,5,6);
Set<Integer> sets2 =Sets.newHashSet(3,4,5,6,7,8,9);
//交集
System.out.println("交集为:");
SetView<Integer> intersection = Sets.intersection(sets, sets2);
for (Integer integer : intersection) {
System.out.println(integer);
}
//差集
System.out.println("差集为:");
SetView<Integer> diff =Sets.difference(sets, sets2);
for(Integer temp:diff){
System.out.println(temp);
}
//并集
System.out.println("并集为:");
SetView<Integer> union =Sets.union(sets, sets2);
for(Integer temp:union){
System.out.println(temp);
}
}
}- Multiset MultiMap BiMap
Multiset:
import java.util.Set;
import com.google.common.collect.HashMultiset;
import com.google.common.collect.Multiset;
/**
* 统计单词出现的次数
* Multiset 无序 可重复 .count 增强了可读性 操作简单
* @author Matrix42
*
*/
public class Demo02 {
public static void main(String[] args) {
String str ="this is a cat and that is a mice where is the food";
//分割字符串
String[] strArray = str.split(" ");
//存储到Multiset
Multiset<String> set = HashMultiset.create();
for (String string : strArray) {
set.add(string);
}
//获取所有的单词
Set<String> letters = set.elementSet();
for (String string : letters) {
System.out.println(string+"--->"+set.count(string));
}
}
}MultiMap:
import java.util.Collection;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
import com.google.common.collect.ArrayListMultimap;
import com.google.common.collect.Multimap;
/**
* 分析查看 教师 教授的没门课程
* MultiMap key-value key可以重复
* @author Matrix42
*
*/
public class Demo03 {
public static void main(String[] args) {
Map<String, String> cours = new HashMap<>();
//加入测试数据
cours.put("改革开放", "邓小平");
cours.put("三个代表", "江泽民");
cours.put("科学发展观", "胡锦涛");
cours.put("和谐社会", "胡锦涛");
cours.put("八荣八耻", "胡锦涛");
cours.put("...", "习近平");
//Multimap
Multimap<String,String> teachers = ArrayListMultimap.create();
Iterator<Map.Entry<String, String>> it = cours.entrySet().iterator();
while(it.hasNext()){
Map.Entry<String, String> entry = it.next();
String key = entry.getKey();
String value = entry.getValue();
//教师 -- 课程
teachers.put(value, key);
}
//查看Multimap
Set<String> leyset = teachers.keySet();
for (String string : leyset) {
Collection<String> col = teachers.get(string);
System.out.println(string+"-->"+col);
}
}
}BiMap:
import com.google.common.collect.BiMap;
import com.google.common.collect.HashBiMap;
/**
* HashMap 键唯一,值可以重复
* BiMap:双向Map(Bidirectional Map ) 键与值都不能重复(unique -valued map)
* @author Matrix42
*
*/
public class Demo04 {
public static void main(String[] args) {
BiMap<String, String> biMap = HashBiMap.create();
biMap.put("lorinda", "admin@lorinda.cc");
biMap.put("Matrix42", "admin@sundeqiang.cn");
//通过邮箱找用户
String user = biMap.inverse().get("admin@lorinda.cc");
System.out.println(user);
System.out.println(biMap.inverse().inverse().get(user));
}
}* Table
import java.util.Map;
import java.util.Set;
import com.google.common.collect.HashBasedTable;
import com.google.common.collect.Table;
import com.google.common.collect.Table.Cell;
import com.google.common.collect.Tables;
/**
* 双键的Map -->Table -->rowKey+columnKey+value
* * 1、方法
* 所有的行数据:cellSet()
* 所有的学生: rowKeySet()
* 所有的课程:columnKeySet()
* 所有的成绩: values()
* 学生对应的课程: rowMap() +get(学生)
* row(学生)
* 课程对应的学生: columnMap +get(课程)
* column(课程)
* @author Matrix42
*
*/
public class Demo08 {
public static void main(String[] args) {
Table<String, String, Integer> tables = HashBasedTable.create();
//测试数据
tables.put("a", "javase", 80);
tables.put("b", "javase", 90);
tables.put("a", "oracle", 100);
tables.put("c", "oracle", 95);
//所有行数据
Set<Cell<String, String, Integer>> cells = tables.cellSet();
for (Cell<String, String, Integer> cell : cells) {
System.out.println(cell.getRowKey()+"-->"+cell.getColumnKey()+"-->"+cell.getValue());
}
System.out.println("==============学生查看成绩=============");
System.out.print("学生\t");
//所有课程
Set<String> cours = tables.columnKeySet();
for (String string : cours) {
System.out.print(string+"\t");
}
System.out.println();
//所有学生
Set<String> stus = tables.rowKeySet();
for (String string : stus) {
System.out.print(string+"\t");
Map<String, Integer> scores = tables.row(string);
for (String string2 : cours) {
System.out.print(scores.get(string2)+"\t");
}
System.out.println();
}
//所有的学生
Set<String> stus1 =tables.rowKeySet();
for(String stu:stus1){
System.out.print(stu+"\t");
Map<String,Integer> scores =tables.row(stu);
for(String c:cours){
System.out.print(scores.get(c)+"\t");
}
System.out.println();
}
System.out.println("==========课程查看成绩==============");
System.out.print("课程\t");
//所有的学生
Set<String> stuSet =tables.rowKeySet();
for(String t:stuSet){
System.out.print(t+"\t");
}
System.out.println();
//所有的课程
Set<String> courSet =tables.columnKeySet();
for(String c:courSet){
System.out.print(c+"\t");
Map<String,Integer> scores =tables.column(c);
for(String s:stuSet){
System.out.print(scores.get(s)+"\t");
}
System.out.println();
}
System.out.println("===========转换===========");
Table<String,String,Integer> tables2 =Tables.transpose(tables);
//所有的行数据
Set<Cell<String,String,Integer>> cells2 =tables2.cellSet();
for(Cell<String,String,Integer> temp:cells2){
System.out.println(temp.getRowKey()+"-->"+temp.getColumnKey()+"-->"+temp.getValue());
}
}
}