92 lines
2.4 KiB
Java
92 lines
2.4 KiB
Java
// onjava/CountMap.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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// Unlimited-length Map containing sample data
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// {java onjava.CountMap}
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package onjava;
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import java.util.*;
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import java.util.stream.*;
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public class CountMap
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extends AbstractMap<Integer,String> {
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private int size;
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private static char[] chars =
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"ABCDEFGHIJKLMNOPQRSTUVWXYZ".toCharArray();
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private static String value(int key) {
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return
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chars[key % chars.length] +
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Integer.toString(key / chars.length);
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}
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public CountMap(int size) {
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this.size = size < 0 ? 0 : size;
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}
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@Override public String get(Object key) {
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return value((Integer)key);
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}
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private static class Entry
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implements Map.Entry<Integer,String> {
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int index;
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Entry(int index) { this.index = index; }
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@Override public boolean equals(Object o) {
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return o instanceof Entry &&
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Objects.equals(index, ((Entry)o).index);
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}
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@Override public Integer getKey() { return index; }
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@Override public String getValue() {
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return value(index);
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}
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@Override public String setValue(String value) {
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throw new UnsupportedOperationException();
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}
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@Override public int hashCode() {
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return Objects.hashCode(index);
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}
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}
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@Override
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public Set<Map.Entry<Integer,String>> entrySet() {
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// LinkedHashSet retains initialization order:
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return IntStream.range(0, size)
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.mapToObj(Entry::new)
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.collect(Collectors
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.toCollection(LinkedHashSet::new));
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}
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public static void main(String[] args) {
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final int size = 6;
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CountMap cm = new CountMap(60);
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System.out.println(cm);
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System.out.println(cm.get(500));
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cm.values().stream()
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.limit(size)
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.forEach(System.out::println);
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System.out.println();
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new Random(47).ints(size, 0, 1000)
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.mapToObj(cm::get)
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.forEach(System.out::println);
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}
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}
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/* Output:
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{0=A0, 1=B0, 2=C0, 3=D0, 4=E0, 5=F0, 6=G0, 7=H0, 8=I0,
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9=J0, 10=K0, 11=L0, 12=M0, 13=N0, 14=O0, 15=P0, 16=Q0,
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17=R0, 18=S0, 19=T0, 20=U0, 21=V0, 22=W0, 23=X0, 24=Y0,
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25=Z0, 26=A1, 27=B1, 28=C1, 29=D1, 30=E1, 31=F1, 32=G1,
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33=H1, 34=I1, 35=J1, 36=K1, 37=L1, 38=M1, 39=N1, 40=O1,
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41=P1, 42=Q1, 43=R1, 44=S1, 45=T1, 46=U1, 47=V1, 48=W1,
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49=X1, 50=Y1, 51=Z1, 52=A2, 53=B2, 54=C2, 55=D2, 56=E2,
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57=F2, 58=G2, 59=H2}
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G19
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A0
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B0
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C0
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D0
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E0
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F0
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Y9
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J21
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R26
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D33
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Z36
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N16
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*/
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