guava之只读、函数式编程（过滤、转换）

package com.lfj.myguava;import java.util.ArrayList;import java.util.Collections;import java.util.List;import com.google.common.collect.ImmutableList;/** * 只读设置 * @author Administrator * */public class Demo1 {    public static void main(String[] args) {        List<String> list=new ArrayList<String>();        list.add("a");        list.add("b");        list.add("c");        //对原有list进行包装，相等于原有List的一个视图、快照        List<String> readList=Collections.unmodifiableList(list);        //readList.add("d");    //java.lang.UnsupportedOperationException异常        list.add("e");  //改变原有List  视图也一起改变        //对比查看 初始化List，且不可再改变        List<String> list1=ImmutableList.of("a","b","c");        //list1.add("e");  添加失败    }}

    package com.lfj.myguava;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 * 1.Predicate  断言 * 2.Function *  * 工具：Collections2.filter 过滤器 * Collections2.transform  转换 * @author Administrator * */public class Demo2 {    public static void main(String[] args) {        //创建List 静态初始化        List<String> list=Lists.newArrayList("son","dad","moom","refer");        //找出回文 palindrome        Collection<String> palindromeList =Collections2.filter(list,new Predicate<String>(){            public boolean apply(String input) {                //业务逻辑                return new StringBuilder(input).reverse().toString().equals(input);            }        });        for(String temp:palindromeList){            System.out.println(temp);        }        Set<Long> timeSet=Sets.newHashSet();        timeSet.add(10000000000L);        timeSet.add(4444444444444444L);        timeSet.add(8888888888888L);        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);        }        //组合式编程        //确保容器中的字符串长度不超过5，超过进行截取，后全部大写        List<String> list2=Lists.newArrayList("lfj","happiness","howwww");        Function<String,String> f1=new Function<String, String>() {            @Override            public String apply(String input) {                // TODO Auto-generated method stub                return input.length()>5?input.substring(0,5):input;            }        };        Function<String, String> f2=new Function<String, String>() {            @Override            public String apply(String input) {                // TODO Auto-generated method stub                return input.toUpperCase();            }        };        //组合使用        Function<String,String> f=Functions.compose(f1, f2);        Collection<String> result=Collections2.transform(list2, f);        for (String string : result) {            System.out.println(string);        }    }}

输出：

        dad        moom        refer        142808-11-02        1970-04-27        2251-09-05        LFJ        HAPPI        HOWWW