Java高版本Api在Android中的使用方法详解

android {

   defaultConfig {

     multiDexEnabled true

   }

   compileOptions {

     // Flag to enable support for the new language APIs

     coreLibraryDesugaringEnabled true

     sourceCompatibility JavaVersion.VERSION_1_8

     targetCompatibility JavaVersion.VERSION_1_8

   }

}

dependencies {

   coreLibraryDesugaring 'com.android.tools:desugar_jdk_libs:1.1.5'

}

// 日期

LocalDate today = LocalDate.now();

// 几号

int dayofMonth = today.getDayOfMonth();

// 星期几

int dayofWeek = today.getDayOfWeek().getValue();

// 今年

int dayofYear = today.getDayOfYear();

LocalDate endOfFeb = LocalDate.parse( "2018-02-28" );

         // 取本月第1天：

LocalDate firstDayOfThisMonth = today.with(TemporalAdjusters.firstDayOfMonth());

// 取本月第2天：

LocalDate secondDayOfThisMonth = today.withDayOfMonth( 2 );

// 取本月最后一天，再也不用计算是28，29，30还是31：

LocalDate lastDayOfThisMonth = today.with(TemporalAdjusters.lastDayOfMonth());

// 取下一天：

LocalDate firstDayOfNextMonth = lastDayOfThisMonth.plusDays( 1 );

// 取2017年1月第一个周一：

LocalDate firstMondayOf2017 = LocalDate.parse( "2017-01-01" ).with(TemporalAdjusters.firstInMonth(DayOfWeek.MONDAY));

List<widget> widgets = new ArrayList<>();

       widgets.add( new widget(Color.RED, "Name" , 1 ));

       int sum = widgets.stream()

               .filter(w -> w.getColor() == Color.RED)

               .mapToInt(w -> w.getWeight())

               .sum();

   List<User> userList = Stream.

       of(arrayList).

       map(person -> new User(person.getName())).

       collect(Collectors.toList());

   //peek 和map类似-但是他更强大-它对每个元素执行操作并返回一个新的 Stream

   Stream.of( "one" , "two" , "three" , "four" )

   .filter(e -> e.length() > 3 )

   .peek(e -> System.out.println( "Filtered value: " + e))

   .map(String::toUpperCase)

   .peek(e -> System.out.println( "Mapped value: " + e))

   .collect(Collectors.toList());

   //limit 返回 Stream 的前面 n 个元素；

   //skip 则是扔掉前 n 个元素

   List<String> personList2 = persons.stream()

   .map(Person::getName)

   .limit( 10 )

   .skip( 3 )

   .collect(Collectors.toList());

   System.out.println(personList2);

...

  repositories {

      maven { url 'https://maven.aliyun.com/nexus/content/groups/public/' }

      google()

      maven { url 'https://jitpack.io' }

      mavenCentral()

      jcenter()

  }

  dependencies {

      classpath 'com.android.tools.build:gradle:7.0.3'

      classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"

      classpath 'com.google.gms:google-services:4.3.8'

  }

...

android {

   defaultConfig {

     multiDexEnabled true

   }

   compileOptions {

     // Flag to enable support for the new language APIs

     coreLibraryDesugaringEnabled true

     sourceCompatibility JavaVersion.VERSION_1_8

     targetCompatibility JavaVersion.VERSION_1_8

   }

}

dependencies {

   coreLibraryDesugaring 'com.android.tools:desugar_jdk_libs:1.1.5'

}