90 lines
2.4 KiB
Java
90 lines
2.4 KiB
Java
// patterns/chain/ChainOfResponsibility.java
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// (c)2017 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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// Using the Functional interface
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// {java patterns.chain.ChainOfResponsibility}
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package patterns.chain;
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import java.util.*;
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import java.util.function.*;
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class Result {
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boolean success;
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List<Double> line;
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public Result(List<Double> data) {
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success = true;
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line = data;
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}
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public Result() {
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success = false;
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line = Collections.<Double>emptyList();
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}
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}
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class Fail extends Result {}
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interface Algorithm {
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Result algorithm(List<Double> line);
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}
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class FindMinima {
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public static Result leastSquares(List<Double> line) {
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System.out.println("LeastSquares.algorithm");
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boolean weSucceed = false;
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if(weSucceed) // Actual test/calculation here
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return new Result(Arrays.asList(1.1, 2.2));
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else // Try the next one in the chain:
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return new Fail();
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}
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public static Result perturbation(List<Double> line) {
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System.out.println("Perturbation.algorithm");
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boolean weSucceed = false;
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if(weSucceed) // Actual test/calculation here
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return new Result(Arrays.asList(3.3, 4.4));
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else
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return new Fail();
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}
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public static Result bisection(List<Double> line) {
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System.out.println("Bisection.algorithm");
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boolean weSucceed = true;
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if(weSucceed) // Actual test/calculation here
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return new Result(Arrays.asList(5.5, 6.6));
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else
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return new Fail();
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}
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static List<Function<List<Double>, Result>> algorithms =
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Arrays.asList(
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FindMinima::leastSquares,
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FindMinima::perturbation,
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FindMinima::bisection
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);
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public static Result minima(List<Double> line) {
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for(Function<List<Double>, Result> alg : algorithms) {
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Result result = alg.apply(line);
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if(result.success)
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return result;
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}
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return new Fail();
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}
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}
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public class ChainOfResponsibility {
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public static void main(String[] args) {
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FindMinima solver = new FindMinima();
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List<Double> line = Arrays.asList(
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1.0, 2.0, 1.0, 2.0, -1.0,
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3.0, 4.0, 5.0, 4.0);
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Result result = solver.minima(line);
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if(result.success)
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System.out.println(result.line);
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else
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System.out.println("No algorithm found");
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}
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}
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/* Output:
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LeastSquares.algorithm
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Perturbation.algorithm
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Bisection.algorithm
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[5.5, 6.6]
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*/
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