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TOVAL comprises a set of java classes for common programming issues. It includes utils for arrays, lists, sets and collections for convenient handling and modification, but also support for mathematic definitions concerning logic (clauses + resolution) together with some algorithms for permutations, powersets and resolution. Additionally it contains a number of types for multisets, matrices with object keys and much more.

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package de.invation.code.toval.constraint;

import de.invation.code.toval.validate.ParameterException;
import de.invation.code.toval.validate.Validate;
import de.invation.code.toval.validate.ParameterException.ErrorCode;

public enum StringOperator implements Operator {
	
	EQUAL(OperatorFormats.EQUAL, String.format(OperatorFormats.COMPARISON_FORMAT, OperatorFormats.EQUAL)), 
	NOT_EQUAL(OperatorFormats.NOT_EQUAL, String.format(OperatorFormats.COMPARISON_FORMAT, OperatorFormats.NOT_EQUAL));
	
	private String[] argumentNames = new String[] {"Attribute", "Comparator"};
	private String sign = null;
	private String toStringFormat = null;
	
	private StringOperator(String sign, String toStringFormat){
		this.sign = sign;
		this.toStringFormat = toStringFormat;
	}
	
	private StringOperator(String[] arguments, String sign, String toStringFormat){
		this(sign, toStringFormat);
		this.argumentNames = arguments;
	}

	@Override
	public int getRequiredArguments(){
		return argumentNames.length;
	}
	
	@Override
	public String[] getArgumentNames(){
		return argumentNames;
	}
	
	protected void validateValueType(Object value) throws ParameterException{
		if(!String.class.isAssignableFrom(value.getClass()))
			throw new ParameterException(ErrorCode.TYPE, "Wrong type of validation value, expected type: " + String.class);
	}
	
	@Override
	public boolean validate(Object value, String... parameters) throws ParameterException {
		Validate.notNull(value);
		validateValueType(value);
		Validate.notNull(parameters);
		Validate.noNullElements(parameters);
		Validate.isFalse(parameters.length + 1 != getRequiredArguments());
		
		switch(this){
		case EQUAL:			return value.equals(parameters[0]);
		case NOT_EQUAL:		return !value.equals(parameters[0]);
		default: return false;
		}
	}
	
	@Override
	public String getStringFormat(){
		return toStringFormat;
	}
	
	@Override
	public String toString(){
		return sign;
	}
	
	public static StringOperator parse(String operatorString){
		if(operatorString.equals("=="))
			return StringOperator.EQUAL;
		if(operatorString.equals("!="))
			return StringOperator.NOT_EQUAL;
		return null;
	}
	
	
	
}