Java设计模式

code/Java/design-pattern/src/main/java/com/heibaiying/behavioral/interpreter/AddExpression.java

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+package com.heibaiying.behavioral.interpreter;
+
+import java.util.HashMap;
+
+public class AddExpression extends SymbolExpression {
+	public AddExpression(Expression left, Expression right) {
+		super(left, right);
+	}
+
+	//把左右两个表达式运算的结果加起来
+	public int interpreter(HashMap<String, Integer> var) {
+		return super.left.interpreter(var) + super.right.interpreter(var);
+	}
+}

code/Java/design-pattern/src/main/java/com/heibaiying/behavioral/interpreter/Calculator.java

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+package com.heibaiying.behavioral.interpreter;
+
+import java.util.HashMap;
+import java.util.Stack;
+
+public class Calculator {
+	//定义表达式
+	private Expression expression;
+
+	//构造函数传参，并解析
+	public Calculator(String expStr) {
+		//定义一个栈，安排运算的先后顺序
+		Stack<Expression> stack = new Stack<>();
+		//表达式拆分为字符数组
+		char[] charArray = expStr.toCharArray();
+		//运算
+		Expression left;
+		Expression right;
+		for (int i = 0; i < charArray.length; i++) {
+			switch (charArray[i]) {
+				case '+': //加法
+					//加法结果放到栈中
+					left = stack.pop();
+					right = new VarExpression(String.valueOf(charArray[++i]));
+					stack.push(new AddExpression(left, right));
+					break;
+				case '-':
+					left = stack.pop();
+					right = new VarExpression(String.valueOf(charArray[++i]));
+					stack.push(new SubExpression(left, right));
+					break;
+				default: //公式中的变量
+					stack.push(new VarExpression(String.valueOf(charArray[i])));
+			}
+		}
+		//把运算结果抛出来
+		this.expression = stack.pop();
+	}
+
+	//开始运算
+	public int run(HashMap<String, Integer> var) {
+		return this.expression.interpreter(var);
+	}
+}

code/Java/design-pattern/src/main/java/com/heibaiying/behavioral/interpreter/Expression.java

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+package com.heibaiying.behavioral.interpreter;
+
+import java.util.HashMap;
+
+public abstract class Expression {
+	//解析公式和数值，其中var中的key值是公式中的参数，value值是具体的数字
+	public abstract int interpreter(HashMap<String, Integer> var);
+}

code/Java/design-pattern/src/main/java/com/heibaiying/behavioral/interpreter/SubExpression.java

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+package com.heibaiying.behavioral.interpreter;
+
+import java.util.HashMap;
+
+public class SubExpression extends SymbolExpression {
+	public SubExpression(Expression left,Expression right){
+		super(left,right);
+	}
+	//左右两个表达式相减
+	public int interpreter(HashMap<String, Integer> var) {
+		return super.left.interpreter(var) - super.right.interpreter(var);
+	}
+}

code/Java/design-pattern/src/main/java/com/heibaiying/behavioral/interpreter/SymbolExpression.java

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+package com.heibaiying.behavioral.interpreter;
+
+public abstract class SymbolExpression extends Expression {
+	protected Expression left;
+	protected Expression right;
+
+	//所有的解析公式都应只关心自己左右两个表达式的结果
+	public SymbolExpression(Expression left, Expression right) {
+		this.left = left;
+		this.right = right;
+	}
+}

code/Java/design-pattern/src/main/java/com/heibaiying/behavioral/interpreter/VarExpression.java

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+package com.heibaiying.behavioral.interpreter;
+
+import java.util.HashMap;
+
+public class VarExpression extends Expression {
+
+	private String key;
+
+	public VarExpression(String key) {
+		this.key = key;
+	}
+
+	//从map中取之
+	public int interpreter(HashMap<String, Integer> var) {
+		return var.get(this.key);
+	}
+}

code/Java/design-pattern/src/main/java/com/heibaiying/behavioral/interpreter/ZTest.java

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+package com.heibaiying.behavioral.interpreter;
+
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.util.HashMap;
+
+public class ZTest {
+	//运行四则运算
+	public static void main(String[] args) throws IOException {
+		String expStr = getExpStr();
+		//赋值
+		HashMap<String, Integer> var = getValue(expStr);
+		Calculator cal = new Calculator(expStr);
+		System.out.println("运算结果为：" + expStr + "=" + cal.run(var));
+	}
+
+	//获得表达式
+	public static String getExpStr() throws IOException {
+		System.out.print("请输入表达式：");
+		return (new BufferedReader(new InputStreamReader(System.in))).readLine();
+	}
+
+	//获得值映射
+	public static HashMap<String, Integer> getValue(String exprStr) throws IOException {
+		HashMap<String, Integer> map = new HashMap<String, Integer>();
+		//解析有几个参数要传递
+		for (char ch : exprStr.toCharArray()) {
+			if (ch != '+' && ch != '-') {
+				//解决重复参数的问题
+				if (!map.containsKey(String.valueOf(ch))) {
+					String in = (new BufferedReader(new InputStreamReader(System.in))).readLine();
+					map.put(String.valueOf(ch), Integer.valueOf(in));
+				}
+			}
+		}
+		return map;
+	}
+}

code/Java/design-pattern/src/main/java/com/heibaiying/behavioral/iterator/Book.java

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+package com.heibaiying.behavioral.iterator;
+
+import lombok.Data;
+
+@Data
+public class Book {
+	private String name;
+
+	public Book(String name) {
+		this.name = name;
+	}
+
+}

code/Java/design-pattern/src/main/java/com/heibaiying/behavioral/iterator/BookIterator.java

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+package com.heibaiying.behavioral.iterator;
+
+import java.util.List;
+
+public class BookIterator implements Iterator<Book> {
+
+	private List<Book> bookList;
+	private int position = 0;
+
+	public BookIterator(List<Book> bookList) {
+		this.bookList = bookList;
+	}
+
+	@Override
+	public Book next() {
+		return bookList.get(position++);
+	}
+
+	@Override
+	public boolean hasNext() {
+		return position < bookList.size();
+	}
+}

code/Java/design-pattern/src/main/java/com/heibaiying/behavioral/iterator/Bookshelf.java

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+package com.heibaiying.behavioral.iterator;
+
+/**
+ * 书柜
+ */
+public interface Bookshelf {
+
+	void addBook(Book book);
+
+	void removeBook(Book book);
+
+	BookIterator iterator();
+}

code/Java/design-pattern/src/main/java/com/heibaiying/behavioral/iterator/BookshelfImpl.java

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+package com.heibaiying.behavioral.iterator;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * 书柜
+ */
+public class BookshelfImpl implements Bookshelf {
+
+	private List<Book> bookList = new ArrayList<>();
+
+	@Override
+	public void addBook(Book book) {
+		bookList.add(book);
+	}
+
+	@Override
+	public void removeBook(Book book) {
+		bookList.remove(book);
+	}
+
+	@Override
+	public BookIterator iterator() {
+		return new BookIterator(bookList);
+	}
+}

code/Java/design-pattern/src/main/java/com/heibaiying/behavioral/iterator/Iterator.java

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+package com.heibaiying.behavioral.iterator;
+
+public interface Iterator<E> {
+	E next();
+	boolean hasNext();
+}

code/Java/design-pattern/src/main/java/com/heibaiying/behavioral/iterator/ZTest.java

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+package com.heibaiying.behavioral.iterator;
+
+public class ZTest {
+	public static void main(String[] args) {
+		BookshelfImpl bookshelf = new BookshelfImpl();
+		bookshelf.addBook(new Book("Java书籍"));
+		bookshelf.addBook(new Book("Python书籍"));
+		bookshelf.addBook(new Book("Go书籍"));
+		BookIterator iterator = bookshelf.iterator();
+		while (iterator.hasNext()) {
+			System.out.println(iterator.next());
+		}
+	}
+}

code/Java/design-pattern/src/main/java/com/heibaiying/behavioral/observer/Business.java

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+package com.heibaiying.behavioral.observer;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class Business implements Observable {
+
+	private List<Observer> observerList = new ArrayList<>();
+
+	@Override
+	public void addObserver(Observer observer) {
+		observerList.add(observer);
+	}
+
+	@Override
+	public void removeObserver(Observer observer) {
+		observerList.remove(observer);
+	}
+
+	@Override
+	public void notifyObservers(String message) {
+		for (Observer observer : observerList) {
+			observer.receive(message);
+		}
+	}
+}

code/Java/design-pattern/src/main/java/com/heibaiying/behavioral/observer/Observable.java

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+package com.heibaiying.behavioral.observer;
+
+public interface Observable {
+
+	void addObserver(Observer observer);
+
+	void removeObserver(Observer observer);
+
+	void notifyObservers(String message);
+}

code/Java/design-pattern/src/main/java/com/heibaiying/behavioral/observer/Observer.java

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+package com.heibaiying.behavioral.observer;
+
+public interface Observer {
+	void receive(String message);
+}

code/Java/design-pattern/src/main/java/com/heibaiying/behavioral/observer/User.java

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+package com.heibaiying.behavioral.observer;
+
+import lombok.Data;
+
+@Data
+public class User implements Observer {
+
+	private String name;
+
+	public User(String name) {
+		this.name = name;
+	}
+
+	@Override
+	public void receive(String message) {
+		System.out.println(getName() + "收到消息：" + message);
+	}
+}

code/Java/design-pattern/src/main/java/com/heibaiying/behavioral/observer/ZTest.java

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+package com.heibaiying.behavioral.observer;
+
+public class ZTest {
+
+	public static void main(String[] args) {
+		Business business = new Business();
+		business.addObserver(new User("用户1"));
+		business.addObserver(new User("用户2"));
+		business.addObserver(new User("用户3"));
+		business.notifyObservers("商品促销通知");
+	}
+
+}

code/Java/design-pattern/src/main/java/com/heibaiying/behavioral/strategy/BonusStrategy.java

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+package com.heibaiying.behavioral.strategy;
+
+public class BonusStrategy implements Strategy {
+	@Override
+	public void execute() {
+		System.out.println("奖金激励");
+	}
+}

code/Java/design-pattern/src/main/java/com/heibaiying/behavioral/strategy/Company.java

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+package com.heibaiying.behavioral.strategy;
+
+public class Company {
+
+	private Strategy strategy;
+
+	public Company setStrategy(Strategy strategy) {
+		this.strategy = strategy;
+		return this;
+	}
+
+	public void execute() {
+		strategy.execute();
+	}
+}

code/Java/design-pattern/src/main/java/com/heibaiying/behavioral/strategy/Strategy.java

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+package com.heibaiying.behavioral.strategy;
+
+public interface Strategy {
+	void execute();
+}

code/Java/design-pattern/src/main/java/com/heibaiying/behavioral/strategy/TravelStrategy.java

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+package com.heibaiying.behavioral.strategy;
+
+public class TravelStrategy implements Strategy {
+	@Override
+	public void execute() {
+		System.out.println("集体旅游");
+	}
+}

code/Java/design-pattern/src/main/java/com/heibaiying/behavioral/strategy/WorkOvertimeStrategy.java

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+package com.heibaiying.behavioral.strategy;
+
+public class WorkOvertimeStrategy implements Strategy {
+	@Override
+	public void execute() {
+		System.out.println("奖励加班");
+	}
+}

code/Java/design-pattern/src/main/java/com/heibaiying/behavioral/strategy/ZTest.java

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+package com.heibaiying.behavioral.strategy;
+
+public class ZTest {
+	public static void main(String[] args) {
+		// 营业额
+		int turnover = Integer.parseInt(args[0]);
+		Company company = new Company();
+		if (turnover > 1000) {
+			company.setStrategy(new BonusStrategy()).execute();
+		} else if (turnover > 100) {
+			company.setStrategy(new TravelStrategy()).execute();
+		} else {
+			company.setStrategy(new WorkOvertimeStrategy()).execute();
+		}
+	}
+}