Cleaned up Hash#fetch impl in JRuby

gistfile1.java

    @JRubyMethod(compat = RUBY1_9)
    public IRubyObject fetch(ThreadContext context, IRubyObject key, Block block) {
        Ruby runtime = context.runtime;

        IRubyObject value = internalGet(key);
        
        if (value == null) {
            if (block.isGiven()) return block.yield(context, key);
            
            throw runtime.newKeyError("key not found: " + key);
        }
        
        return value;
    }
    
    @JRubyMethod(compat = RUBY1_9)
    public IRubyObject fetch(ThreadContext context, IRubyObject key, IRubyObject _default, Block block) {
        Ruby runtime = context.runtime;
        boolean blockGiven = block.isGiven();

        if (blockGiven) {
            runtime.getWarnings().warn(ID.BLOCK_BEATS_DEFAULT_VALUE, "block supersedes default value argument");
        }

        IRubyObject value = internalGet(key);
        
        if (value == null) {
            if (blockGiven) return block.yield(context, key);
            
            return _default;
        }
        
        return value;
    }

Yes, this reads great.