Custom button to add existing records In org.

I am trying to add a custom button to add existing records to a custom object related list (Specifications(custom obj) to Products(custom obj))

Ext class code:

public with sharing class AddExistingSpecsExt {

public Product__c specs { get; set; }

public AddExistingSpecsExt() {

String specs Specification__c = ApexPages.currentPage().getParameters().get('id');
specs = [SELECT Id, Name, Product__c FROM specs WHERE Id =: specs.Id];

}

public PageReference associate () {

Opportunity opp = new Opportunity ( Id = Specification__c.Product__c, specsid = Specification__c.Id);

try {
Database.update(opp);
} catch (Exception error) {
ApexPages.addMessage(new ApexPages.Message(ApexPages.Severity.ERROR, 'Error while associating.' + error.getMessage()));
}

PageReference page = new PageReference('/' + specs.Id);

return page.setRedirect(true);
}

public PageReference cancel () {
PageReference page = new PageReference('/' + specs.Id);
return page.setRedirect(true);
}

}
I am getting this error:

Line 7: expecting a semi-colon, found 'Specification__c'