• Method signatures are too long (5 parms!)
• All method are statics, possible indication of a God Class
• No flexibility considering that you want ...a common validation class which can be used for in any of my applications"
• Validation options and user credentials are mixed (too many concerns)
• Usage: you instantiate the validator, set the validation settings (maybe a Factory method would do it for you, you can even read the validation settings from a conf file) then call validate(userCredentials);

My suggestion is:

• A PasswordValidator class or interface which is responsible of validation options and performing validation
• A credentials class or interface that holds username, new password, etc.

public interface Credentials {
    public void setUserName(String userName);
    public void setOldPasssword(String oldPassword);
    public void setNewPassword(String newPassword);
    public void setConfirmedNewPassword(String confirmedNewPassword);
    public String getUserName();
    public String getOldPasssword();
    public String getNewPassword();
    public String getConfirmedNewPassword();
 
}

public class ValidationResult {
 
}

public class NicePasswordValidator implements PasswordValidator {
    
    private boolean allowSpecialCharacters;
    private boolean allowPasswordEqualsName;
    private int minimalLength;
    private boolean reset;  
    
    private static boolean containSpecialCharacters(String newPassword) {
        // TODO Auto-generated method stub
        return false;
    }

    private static boolean containsLowerCase(String newPassword) {
        // TODO Auto-generated method stub
        return false;
    }

    private static boolean containsUpperCase(String newPassword) {
        // TODO Auto-generated method stub
        return false;
    }

    private static boolean doesNotContainUpperCaseAlpha(String newPassword) {
        // TODO Auto-generated method stub
        return false;
    }

 

    @Override
    public void setReset(boolean reset) {
        this.reset=reset;
    }

    @Override
    public void setMinimalLength(int length) {
        this.minimalLength=length;
    }

    @Override
    public void setAllowPasswordEqualsName(boolean allow) {
        this.allowPasswordEqualsName=allow;
    }
    
    @Override
    public void setAllowSpecialCharacters(boolean allow) {
        this.allowSpecialCharacters=allow;      
    }   
 

    @Override
    public boolean getReset() {
        return this.reset;
    }

    @Override
    public int getMinimalLength() {
        return this.minimalLength;
    }

    @Override
    public boolean getAllowPasswordEqualsName() {
        return this.allowPasswordEqualsName;
    }

    @Override
    public boolean getAllowSpecialCharacters() {
        return this.allowSpecialCharacters;
    }

    @Override
    public ValidationResult validate(Credentials cred) {
        
        ValidationResult result = new ValidationResult();
        
        if (!this.allowPasswordEqualsName && cred.getNewPassword().endsWith(cred.getUserName())){
            // add to result
        }
        
        if (!cred.getNewPassword().equals(cred.getConfirmedNewPassword())){
            // add to result
        }
        
        if (!this.containsUpperCase(cred.getNewPassword())){
            // add to result
        }
        
        if (!this.containsLowerCase(cred.getNewPassword())){
            // add to result
        }
        
        if (!this.getAllowSpecialCharacters() && this.containSpecialCharacters(cred.getNewPassword())){
            // add to result
        }
        
        return result;
    }
}

• Method signatures are too long (5 parms!)
• All method are statics, possible indication of a God Class
• No flexibility considering that you want ...a common validation class which can be used for in any of my applications"
• Validation options and user credentials are mixed (too many concerns)

My suggestion is:

• A PasswordValidator class or interface which is responsible of validation options and performing validation
• A credentials class or interface that holds username, new password, etc.
• Usage: you instantiate the validator, set the validation settings (maybe a Factory method would do it for you, you can even read the validation settings from a conf file) then call validate(userCredentials);

One PNG is worth 1024 words:

public interface Credentials {
    public void setUserName(String userName);
    public void setOldPasssword(String oldPassword);
    public void setNewPassword(String newPassword);
    public void setConfirmedNewPassword(String confirmedNewPassword);
    public String getUserName();
    public String getOldPasssword();
    public String getNewPassword();
    public String getConfirmedNewPassword();
}

public class ValidationResult {
}

public class NicePasswordValidator implements PasswordValidator {
    
    private boolean allowSpecialCharacters;
    private boolean allowPasswordEqualsName;
    private int minimalLength;
    private boolean reset;  
    
    private static boolean containSpecialCharacters(String newPassword) {
        // TODO Auto-generated method stub
        return false;
    }

    private static boolean containsLowerCase(String newPassword) {
        // TODO Auto-generated method stub
        return false;
    }

    private static boolean containsUpperCase(String newPassword) {
        // TODO Auto-generated method stub
        return false;
    }

    private static boolean doesNotContainUpperCaseAlpha(String newPassword) {
        // TODO Auto-generated method stub
        return false;
    }

    @Override
    public void setReset(boolean reset) {
        this.reset=reset;
    }

    @Override
    public void setMinimalLength(int length) {
        this.minimalLength=length;
    }

    @Override
    public void setAllowPasswordEqualsName(boolean allow) {
        this.allowPasswordEqualsName=allow;
    }
    
    @Override
    public void setAllowSpecialCharacters(boolean allow) {
        this.allowSpecialCharacters=allow;      
    }   

    @Override
    public boolean getReset() {
        return this.reset;
    }

    @Override
    public int getMinimalLength() {
        return this.minimalLength;
    }

    @Override
    public boolean getAllowPasswordEqualsName() {
        return this.allowPasswordEqualsName;
    }

    @Override
    public boolean getAllowSpecialCharacters() {
        return this.allowSpecialCharacters;
    }

    @Override
    public ValidationResult validate(Credentials cred) {
        
        ValidationResult result = new ValidationResult();
        
        if (!this.allowPasswordEqualsName && cred.getNewPassword().endsWith(cred.getUserName())){
            // add to result
        }
        
        if (!cred.getNewPassword().equals(cred.getConfirmedNewPassword())){
            // add to result
        }
        
        if (!this.containsUpperCase(cred.getNewPassword())){
            // add to result
        }
        
        if (!this.containsLowerCase(cred.getNewPassword())){
            // add to result
        }
        
        if (!this.getAllowSpecialCharacters() && this.containSpecialCharacters(cred.getNewPassword())){
            // add to result
        }
        
        return result;
    }
}