135_容器_guava之_只读_函数式编程(过滤、转换、组合 )_约束_集合

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这里写图片描述

只读设置

Test01_ReadOnly.java

package guava.collection;import java.util.ArrayList;import java.util.Collections;import java.util.List;import com.google.common.collect.ImmutableList;/** * 只读设置 * 1.原始(重新包装)：将需要设置为只读的容器用Collections.unmodifiable_xxx()包装成一个新的容器; * 2.现在(直接创建)：直接用Immutable_xxx.of(元素...)创建一个新的容器 */public class Test01_ReadOnly {    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，相等于原有List的一个视图，快照，不够安全        List<String> readList =Collections.unmodifiableList(list);        readList.add("d");//java.lang.UnsupportedOperationException        list.add("d"); //改变原有List;视图也一起改变        //对比 查看 初始化List 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");//java.lang.UnsupportedOperationException    }}

函数式编程(过滤|转换|组合式编程)

Test02_Function.java

package guava.collection;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     Predicate<T> pre=new Predicate<T>() {        @Override        public boolean apply(T input) {            return false;        }    }; * 2.Function *   Function<F, T> fun=new Function<F, T>() {        @Override        public T apply(F input) {            return null;        }     }; *  * 工具: * Collections2.filter(容器,Predicate) 过滤器 * Collections2.transfer(容器,Function) 转换 * Function newf=Functions.compose(f1,f2...)组合式函数编程 */public class Test02_Function {    public static void main(String[] args) {        test1();//过滤器        test2();//转换        test3();//组合式函数编程    }    /**过滤器*/    public static void test1(){        //创建List;静态初始化        List<String> list =Lists.newArrayList("moom","son","dad","bjsxt","refer");        //找出回文 palindrome; backwords; mirror words        //匿名内部类对象: 匿名内部类，同时创建类对象        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 temp:palindromeList){            System.out.println(temp);        }    }    /**转换*/    public static void test2(){        //类型转换        Set<Long> timeSet =Sets.newHashSet();        timeSet.add(10000000L);        timeSet.add(99999999999999999L);        timeSet.add(2000000000L);        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 temp:timeStrCol){            System.out.println(temp);        }    }    /**     * 组合式函数编程     */    public static void test3(){        //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> list =Lists.newArrayList("bjsxt","good","happiness");        //确保容器中的字符串长度不超过5,超过进行截取        Function<String,String> f1 =new Function<String,String>(){            @Override            public String apply(String input) {                return input.length()>5?input.substring(0,5):input;            }        };        //转成大写        Function<String,String> f2 =new Function<String,String>(){            @Override            public String apply(String input) {                return input.toUpperCase();            }        };        //String =f2(f1(String))        Function<String,String> f =Functions.compose(f1, f2);        Collection<String> resultCol =Collections2.transform(list, f);        for(String temp:resultCol){            System.out.println(temp);        }    }}

加入约束条件

Test03_Constraint.java

package guava.collection;import java.util.Set;import com.google.common.collect.Constraint;import com.google.common.collect.Constraints;import com.google.common.base.Preconditions;import com.google.common.collect.Sets;/** * 加入约束条件:Constraint,Preconditions,Constraints * Constraint<E> constraint=new Constraint<E>() {        @Override        public E checkElement(E element) {        Preconditions.checkNotNull(element);//非空验证        Preconditions.checkArgument(element.length()>=5 && element.length()<=20);//长度验证            return element;        }    }; * Constraints.constrained_xxx(需要约束的容器, constraint);//返回一个容器 */public class Test03_Constraint {    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 5-20为字符串                Preconditions.checkArgument(element.length()>=5 && element.length()<=20);                return element;            }        };        Set<String> cs =Constraints.constrainedSet(sets, constraint);//      cs.add(null); //java.lang.NullPointerException//      cs.add("good"); //java.lang.IllegalArgumentException        cs.add("bjsxt");        for(String str:cs){            System.out.println(str);        }    }}

集合的操作

Test04_GatherOperation.java

package guava.collection;import java.util.Set;import com.google.common.collect.Sets;import com.google.common.collect.Sets.SetView;/** * 集合的操作: * 1. 交集 *    Sets.intersection() * 2. 差集 *    Sets.difference() * 3. 并集 *    Sets.union(); */public class Test04_GatherOperation {    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 temp:intersection){            System.out.println(temp);        }        //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);        }    }}

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