driver-core/src/main/com/mongodb/bulk/UpdateRequest.java
public UpdateRequest multi(final boolean isMulti) {
        if (isMulti && updateType == Type.REPLACE) {
            throw new IllegalArgumentException("Replacements can not be multi");
        }
        this.isMulti = isMulti;
        return this;
    }
public UpdateRequest multi(final boolean isMulti) {
        if (isMulti && updateType == Type.REPLACE) {
            throw new IllegalArgumentException("Replacements can not be multi");
        }
        this.isMulti = isMulti;
        return this;
    }
Sets whether this will update all documents matching the query filter.

@param isMulti whether this will update all documents matching the query filter
@return this