69 lines
1.6 KiB
Java
69 lines
1.6 KiB
Java
// patterns/StateDemo.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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// Basic demonstration of the State pattern.
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class State {
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private State implementation;
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protected State() {}
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public State(State imp) {
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implementation = imp;
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}
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public void change(State newImp) {
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implementation = newImp;
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}
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// Forward method calls to the implementation:
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public void f() { implementation.f(); }
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public void g() { implementation.g(); }
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public void h() { implementation.h(); }
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}
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class Implementation1 extends State {
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@Override public void f() {
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System.out.println("Implementation1.f()");
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}
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@Override public void g() {
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System.out.println("Implementation1.g()");
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}
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@Override public void h() {
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System.out.println("Implementation1.h()");
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}
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}
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class Implementation2 extends State {
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@Override public void f() {
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System.out.println("Implementation2.f()");
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}
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@Override public void g() {
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System.out.println("Implementation2.g()");
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}
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@Override public void h() {
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System.out.println("Implementation2.h()");
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}
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}
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public class StateDemo {
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static void test(State s) {
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s.f();
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s.g();
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s.h();
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}
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public static void main(String[] args) {
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State s = new State(new Implementation1());
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test(s);
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System.out.println("Changing implementation");
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s.change(new Implementation2());
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test(s);
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}
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}
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/* Output:
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Implementation1.f()
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Implementation1.g()
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Implementation1.h()
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Changing implementation
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Implementation2.f()
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Implementation2.g()
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Implementation2.h()
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*/
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