55 lines
1.5 KiB
Java
55 lines
1.5 KiB
Java
// collectiontopics/StreamFillMaps.java
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// (c)2021 MindView LLC: see Copyright.txt
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// We make no guarantees that this code is fit for any purpose.
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// Visit http://OnJava8.com for more book information.
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import java.util.*;
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import java.util.function.*;
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import java.util.stream.*;
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import onjava.*;
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class Letters
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implements Supplier<Pair<Integer,String>> {
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private int number = 1;
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private char letter = 'A';
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@Override public Pair<Integer,String> get() {
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return new Pair<>(number++, "" + letter++);
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}
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}
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public class StreamFillMaps {
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public static void main(String[] args) {
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Map<Integer,String> m =
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Stream.generate(new Letters())
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.limit(11)
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.collect(Collectors
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.toMap(Pair::key, Pair::value));
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System.out.println(m);
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// Two separate Suppliers:
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Rand.String rs = new Rand.String(3);
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Count.Character cc = new Count.Character();
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Map<Character,String> mcs = Stream.generate(
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() -> Pair.make(cc.get(), rs.get()))
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.limit(8)
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.collect(Collectors
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.toMap(Pair::key, Pair::value));
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System.out.println(mcs);
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// A key Supplier and a single value:
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Map<Character,String> mcs2 = Stream.generate(
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() -> Pair.make(cc.get(), "Val"))
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.limit(8)
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.collect(Collectors
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.toMap(Pair::key, Pair::value));
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System.out.println(mcs2);
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}
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}
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/* Output:
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{1=A, 2=B, 3=C, 4=D, 5=E, 6=F, 7=G, 8=H, 9=I, 10=J,
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11=K}
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{b=btp, c=enp, d=ccu, e=xsz, f=gvg, g=mei, h=nne,
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i=elo}
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{p=Val, q=Val, j=Val, k=Val, l=Val, m=Val, n=Val,
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o=Val}
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*/
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