operationfactory.java

简单的计算器程序

package calculate;

import java.util.HashMap;
import java.util.Map;

import calculate.operations.AddSubstractOperation;
import calculate.operations.AntiOperation;
import calculate.operations.BackspaceOperation;
import calculate.operations.BaseOperation;
import calculate.operations.CEOperation;
import calculate.operations.COperation;
import calculate.operations.EqualOperation;
import calculate.operations.LetterOperation;
import calculate.operations.PercentOperation;
import calculate.operations.SqrtOperation;

public abstract class OperationFactory {
	
	private static Map<String, Operation> operations = new HashMap<String, Operation>();
	
	private static DefaultOperation defaultOperation = new DefaultOperation();
	static {
		initalOperations();
	}
	
	private static void initalOperations() {
		operations.put("1", new LetterOperation("1"));
		operations.put("2", new LetterOperation("2"));
		operations.put("3", new LetterOperation("3"));
		operations.put("4", new LetterOperation("4"));
		operations.put("5", new LetterOperation("5"));
		operations.put("6", new LetterOperation("6"));
		operations.put("7", new LetterOperation("7"));
		operations.put("8", new LetterOperation("8"));
		operations.put("9", new LetterOperation("9"));
		operations.put("0", new LetterOperation("0"));
		operations.put(".", new LetterOperation("."));
		
		operations.put("+", new BaseOperation("+"));
		operations.put("-", new BaseOperation("-"));
		operations.put("*", new BaseOperation("*"));
		operations.put("/", new BaseOperation("/"));
		operations.put("=", new EqualOperation());
		operations.put("%", new PercentOperation());
		operations.put("sqrt", new SqrtOperation());
		operations.put("1/x", new AntiOperation());
		operations.put("+/-", new AddSubstractOperation());
		
		operations.put("CE", new CEOperation());
		operations.put("C", new COperation());
		operations.put("Backspace", new BackspaceOperation());
	}
	
	public static Operation getOperation(String input) {
		Operation operation = operations.get(input);
		
		if (operation == null) {
			return defaultOperation;
		} 
		
		return operation;
	}
	
	private static class DefaultOperation implements Operation {
		public void execute(Calculate calculate) {
		}
	}
}