Java 如何同时返回多个不同类型

//: net/mindview/util/TwoTuple.java（Java编程思想_代码_目录）

package net.mindview.util;

public class TwoTuple<A, B> {

  public final A first;

  public final B second;

  public TwoTuple(A a, B b) {

   first = a;

   second = b;

  }

  public String toString() {

   return "(" + first + ", " + second + ")" ;

  }

}

//: net/mindview/util/ThreeTuple.java

package net.mindview.util;

public class ThreeTuple<A,B,C> extends TwoTuple<A,B> {

   public final C third;

   public ThreeTuple(A a, B b, C c) {

     super (a, b);

     third = c;

   }

   public String toString() {

     return "(" + first + ", " + second + ", " + third + ")" ;

   }

}

//: net/mindview/util/FourTuple.java

package net.mindview.util;

public class FourTuple<A,B,C,D> extends ThreeTuple<A,B,C> {

   public final D fourth;

   public FourTuple(A a, B b, C c, D d) {

     super (a, b, c);

     fourth = d;

   }

   public String toString() {

     return "(" + first + ", " + second + ", " +

       third + ", " + fourth + ")" ;

   }

}

//: net/mindview/util/FiveTuple.java

package net.mindview.util;

public class FiveTuple<A,B,C,D,E>

extends FourTuple<A,B,C,D> {

   public final E fifth;

   public FiveTuple(A a, B b, C c, D d, E e) {

     super (a, b, c, d);

     fifth = e;

   }

   public String toString() {

     return "(" + first + ", " + second + ", " +

       third + ", " + fourth + ", " + fifth + ")" ;

   }

}

//: generics/TupleTest.java

import net.mindview.util.*;

class Amphibian {

}

class Vehicle {

}

public class TupleTest {

  static TwoTuple<String, Integer> f() {

   // Autoboxing converts the int to Integer:

   return new TwoTuple<String, Integer>( "hi" , 47 );

  }

  static ThreeTuple<Amphibian, String, Integer> g() {

   return new ThreeTuple<Amphibian, String, Integer>( new Amphibian(), "hi" ,

     47 );

  }

  static FourTuple<Vehicle, Amphibian, String, Integer> h() {

   return new FourTuple<Vehicle, Amphibian, String, Integer>( new Vehicle(),

     new Amphibian(), "hi" , 47 );

  }

  static FiveTuple<Vehicle, Amphibian, String, Integer, Double> k() {

   return new FiveTuple<Vehicle, Amphibian, String, Integer, Double>(

     new Vehicle(), new Amphibian(), "hi" , 47 , 11.1 );

  }

  public static void main(String[] args) {

   TwoTuple<String, Integer> ttsi = f();

   System.out.println(ttsi);

   // ttsi.first = "there"; // Compile error: final

   System.out.println(g());

   System.out.println(h());

   System.out.println(k());

  }

}

import java.util.*;

public class Demo {

     //方法1：返回list

     public static List< int []> returnList(){

         List< int []> list= new ArrayList<>();

         list.add( new int []{ 1 });

         list.add( new int []{ 1 , 2 });

         list.add( new int []{ 1 , 2 , 3 });

         return list;

     }

     //方法2：返回Map，一个Map只能有一种数据类型

     public static Map<String, Integer> returnMap(){

         Map<String,Integer> map = new HashMap<>();

         map.put( "age" , 1 );  //]age[是key，类似于索引，1是索引对应的int值

         map.put( "high" , 30 );

         //System.out.println(map.get("age"));

         Map<String, int []> map1 = new HashMap<>();

         map1.put( "array" , new int []{ 1 , 2 , 3 });

         //System.out.println(Arrays.toString(  map1.get("array") ));

         return map;

     }

     //方法3：一次性返回两种类型的数据，结合了Map和list

     public static List<Map> returnMapList(){

         Map<String,Integer> map = new HashMap<>();

         map.put( "age" , 1 );

         map.put( "high" , 30 );

         Map<String, int []> map1 = new HashMap<>();

         map1.put( "array" , new int []{ 1 , 2 });

         List<Map> listMap = new ArrayList<Map>();

         listMap.add(map);

         listMap.add(map1);

         return listMap;

     }

//测试代码

     public static void main(String[] args){

         //返回list

         List< int []> list1 = returnList();

         System.out.println(Arrays.toString(list1.get( 0 )) + Arrays.toString(list1.get( 1 )) + Arrays.toString(list1.get( 2 )) + "\nreturnlist结束\n" );

         //返回Map，一个Map只能有一种数据类型

         Map<String,Integer> mapTest = returnMap();

         System.out.println( "age = " + mapTest.get( "age" ) + "，   high = " + mapTest.get( "high" ) +  "\nreturnMap结束\n" );

         //一次性返回两种类型的数据，结合了Map和list

         List<Map> list2 = returnMapList();

         System.out.println(list2.get( 0 )  + " , " + list2.get( 1 )  + "\nreturnMapList结束" ); //list2.get(1)是数组的地址

         System.out.print( "调用返回的int和int[]:" );

         Map map0 = list2.get( 0 );

         Map map1 = list2.get( 1 );

         System.out.println( "age = " + map0.get( "age" ) );

         System.out.println( "array = " + Arrays.toString(( int []) map1.get( "array" )));

//      System.out.println(Arrays.toString((int[]) list2.get(1).get("array")));   //调用过程也可以这样写

     }

}